Medical device

from Wikipedia, the free encyclopedia

As medical items, materials and software, among other equipment, referred to be used for therapeutic or diagnostic purposes for people, with the principal intended action in contrast to drugs not pharmacologically, is primarily by metabolism or immunologically, but usually physically or physicochemically. There are over 500,000 different types of medical devices and in-vitro diagnostics on the European internal market (as of 2017).

The distinction between medical devices and pharmaceuticals is important, as market access and marketability are regulated differently.

Legal definition

In Germany, the law on medical devices ( Medical Devices Act - MPG) of August 2, 1994 regulates the trade in medical devices. It serves the national implementation of three European (master) directives ( Directive 90/385 / EEC [active implantable medical devices], Directive 93/42 / EEC [other medical devices] and Directive 98/79 / EC [in vitro diagnostics ]), which were supplemented or changed by later amending directives , most recently with Directive 2007/47 / EC from September 5, 2007 to March 21, 2010. The MPG and its eight executive ordinances also contain further national regulations that mainly concern monitoring medical devices on the market (market surveillance).

Section 3 MPG contains the legal definition / s of the term medical device in No. 1 to 4.

EU definition

Medical devices within the meaning of Directive 93/42 / EEC (repealed by Regulation (EU) 2017/745 ) are all instruments, apparatus, devices, software, materials or other items used individually or in combination, including those specifically designed by the manufacturer for use in diagnostic applications and / or therapeutic purposes and software used for the proper functioning of the medical device, which are intended by the manufacturer for humans for the following purposes:

  • Detecting, preventing, monitoring, treating or alleviating disease;
  • Detecting, monitoring, treating, alleviating or compensating for an injury or disability;
  • Investigation, replacement or modification of the anatomical structure or a physiological process;
  • Conception control

and whose intended main effect in or on the human body is achieved neither by pharmacological or immunological agents nor metabolically , but whose mode of action can be supported by such agents.

Likewise, "products that are specifically intended for cleaning, disinfection or sterilization" of medical devices are considered medical devices, e.g. B. autoclaves , cleaning and disinfection devices or cleaning wipes (see definitions in Article 2 of Regulation (EU) 2017/745 ).

An accessory for a medical device is an item that is not itself a medical device, but is to be used "together with a medical device" according to its intended purpose specified by the manufacturer so that it can be used in accordance with the intended purpose of the medical device as defined by the manufacturer of the medical device. However, accessories are regularly treated like a medical device.

Also, in-vitro diagnostic medical devices are ( § 3 Nr. 4 MPG).

An “Active Medical Device” is a medical device whose operation depends on a power source or other energy source (with the exception of energy generated directly by the human body or by gravity). A product for the, essentially unchanged, transfer of energy, substances or parameters between an active medical device and the patient is not considered an active medical device.

A "custom-made product" is any product that is specially made according to specific design features following a written prescription from a doctor and is intended for exclusive use on a named patient. Series-produced products that need to be modified to meet the specific needs of the doctor or other professional user are not considered custom-made products.

"In-house medical devices" are medical devices including accessories that are manufactured in a health facility in order to be used in the operating facility or in rooms in the immediate vicinity of the operating facility without being placed on the market (transfer to another legal body is considered to be placing on the market ) or meet the requirements of a custom-made product. Medical products from in-house production must meet the basic requirements according to Annex I of Directive 93/42 / EEC and the manufacturer must carry out a conformity assessment procedure in accordance with Directive 93/42 / EEC or the MPG (only the CE mark not necessary). The in-house production is specified in the German Medical Devices Act .

Medical products differ from medicinal products ( Directive 2001/83 / EC ) in that their intended main effect is mainly achieved physically (see also product delimitation ).

Active implantable medical devices ( e.g. cardiac pacemakers ) are regulated by EU Directive 90/385 / EEC, in vitro diagnostics by IVD Directive 98/79 / EC. They are also medical devices, but not within the meaning of Directive (93/42 / EEC); in Germany and Austria they are also regulated by the respective national medical device law.

No medical devices are

National exceptions

Every national legislation has the right, for example for safety reasons, to declare certain medical products to be medicinal products (see also product delimitation ). On the other hand, it is not possible to treat only a certain medical device differently from nationally than according to the EU directives.

In most countries, oral care products (toothpaste, toothbrush, etc.) are considered cosmetics, although they correspond to the definition of medical devices.

German exceptions

In-vivo diagnostics such as contrast media are considered pharmaceuticals according to the German Medicines Act (AMG).

According to German law, toothbrushes are regarded as everyday items and not as medical devices.

Austrian exceptions

Natural healing resources and products made from them are not considered medical devices in Austria.

Exceptions in Sweden

Oral care products are considered medicinal products in Sweden.


A distinction is made between active, non-active and implantable medical devices and in-vitro diagnostics . There is also a division into four classes (I, IIa, IIb and III), depending on the risk of use.

The (non-binding) EU guidelines, which are available in English in the form of the MEDDEV guidelines (e.g. 2.4 Classification of medical devices.)

Active, inactive and implantable medical devices

According to Annex IX of Directive 93/42 / EEC, medical devices are divided into active, non-active and medical devices with a measuring function:

  • Active medical devices are devices operated with the help of an external energy source (electricity, rechargeable battery, battery, thermal or kinetic energy or gas pressure).
  • Non-active medical devices are "passive", work by gravity or are operated with muscle power.
  • Medical devices with a measuring function can be active or inactive; some of them have to be checked regularly.

An implantable medical device can be active; For example, an implantable defibrillator , as it contains a battery and is inserted into the human body through a medical procedure in order to remain there after the procedure. Special guidelines apply to active implantable medical devices. Examples of non-active implantable medical products are endoprostheses or port catheters . A blood glucose meter is an active medical product with a measuring function and at the same time an in-vitro diagnostic device.

Medical devices in Annexes 1, 2 and 3

According to Section 10 of the Medical Devices Operator Ordinance (MPBetreibV), special requirements apply in Germany to certain non-implantable active medical devices, infant incubators and external active components of active implants according to Annex 1 , for example with regard to regular safety checks and documented instruction in the operation of the device. What is decisive is the intended purpose specified by the manufacturer, whether the medical device falls under one of the groups in Appendix 1 to the MPBetreibV. The same applies to medical devices in Appendix 2, which are subject to metrological controls. A medical device book must be kept for Annex 1 and Annex 2 products .

Annex 3 includes all active implantable and selected non-active implantable medical products (heart valves, non-resorbable vascular prostheses and supports, joint replacements for the hip or knee, vertebral body replacement systems and intervertebral disc prostheses and breast implants).

Exceptions apply to automatic external defibrillators that are located in publicly accessible locations and are intended for use by laypeople ( Section 11 of the Medical Device Operator Ordinance).

Classification of medical devices according to the Medical Device Operator Ordinance (examples)
Medical device active Attachment 1 Annex 2 Annex 3 Safety checks Inventory Medical device book
Suction pump x according to manufacturer specifications x
mechanical sphygmomanometer with aneroid manometer x
electronic blood pressure monitor x x according to manufacturer specifications x x
Feeding pump x x x
Implantable cardioverter defibrillator x x
Infusion system
Knee prosthesis x
Surveillance monitor x x x x x x
Syringe pump x x x x x

Risk classification

The classification of a medical device is legally based on the “vulnerability of the human body” by the respective product. This in turn is defined by the intended purpose of the manufacturer with regard to the place of use and the duration of use of his product. The risk class results in the proportion of external control or (external) certification of the conformity assessment procedure (procedure for demonstrating compliance with all legal product requirements) by a notified body, which also increases with increasing class height.

The criteria for the division into four risk classes are:

  • Duration of use (up to 60 minutes, up to 30 days, longer than 30 days)
  • Place of application: degree of invasiveness (invasive, surgically invasive, implantable),
  • Use on the central circulatory system or on the central nervous system
  • Reusable surgical instrument
  • Active medical device (active therapeutic medical device / active diagnostic medical device)
  • Use of biological material from animals or humans

The classes are defined across the EU by Annex IX of Directive 93/42 / EEC. This excludes in-vitro diagnostics and active implantable medical devices.

  • Class I.
No methodological risks
low degree of invasiveness
no or uncritical skin contact
temporary use ≤ 60 minutes
  • Class IIa
Application risk
moderate degree of invasiveness
short-term applications in the body (in the eye, intestinal, in surgically created body orifices)
short-term ≤ 30 days, uninterrupted or repeated use of the same product
  • Class IIb
Increased methodological risk
systemic effects
Long-term applications
non-invasive contraception
long-term ≥ 30 days, otherwise as for short-term
  • Class III corresponds to a high risk potential
Particularly high methodological risk
for long-term drug delivery
Ingredient of animal origin and in the body
direct application to the heart, central circulatory system or central nervous system
invasive contraception

For the assessment of compliance with all medical device regulations, the presumption of conformity applies if the requirements of all harmonized standards are observed ( Section 8 of the Medical Devices Act). If the applicable harmonized standards are not complied with, the equivalence of the chosen solution with the harmonized standard must be demonstrated.

The classification rules are detailed in Appendix IX of EU Directive 93/42 / EEC. The application of the classification rules depends on the intended use of the products (and is therefore the responsibility of the manufacturer).


Some specific examples for the classification of medical devices are:

Class I. Class IIa Class IIb Class III

It should be noted however, such a classification is made of medical devices that neither the EU Directives or by national legislation, since in each case, referring in each individual case on its intended use ( intended use , the classification is to be performed).

Classification for processing

The Medical Device Operator Ordinance requires proper reprocessing. To this end, the Commission for Hospital Hygiene and Infection Prevention (KRINKO), the Robert Koch Institute (RKI) and the Federal Institute for Drugs and Medical Devices (BfArM) issued a joint recommendation. Then reusable devices and instruments are divided into non-critical, semi-critical and critical medical devices. The intended use of the respective product is decisive for the classification.

If the product only comes into contact with intact skin, it is considered uncritical; often only cleaning or disinfection is necessary. Semi-critical products come into contact with mucous membranes or pathologically altered skin, so when reprocessing they must always be cleaned and disinfected (semi-critical A), in some cases also cleaned and pre-cleaned immediately after use, then mechanically cleaned and disinfected or sterilized (semi-critical B) if possible . In contrast, critical medical products that penetrate the skin or mucous membrane must always be sterilized. Depending on whether there are cavities or parts that are difficult to access, the reprocessing influences the function and safety of the medical device or the number of reprocessing cycles is limited, the critical medical device is assigned to reprocessing levels A, B or C with the appropriate procedure.

Legal regulations

Implementation in national laws

In every country of the European Union and in the associated countries, the EU directives have been implemented through national laws:

Qualitative regulations on medical devices are met by medical device law. In Germany and Austria, the EU directives are implemented through the National Medical Devices Act (MPG).

With the amendment of EU medical device law in the form of an EU regulation instead of an EU directive as before , national legal implementations within the countries of the EU will no longer apply.

In Switzerland, medical devices are regulated by the Therapeutic Products Act (which is closely based on EU directives).

Conformity assessment procedure

In order to obtain market access authorization for a new medical device for the first time it is placed on the market (import, distribution, etc.), extensive tests must be carried out:

According to § 6 Paragraph 1 MPG, medical devices, with the exception of custom-made products, medical devices manufactured in-house, medical devices in accordance with § 11 Paragraph 1 (special provisions in the interests of health protection) and medical devices used for clinical testing or in vitro diagnostics used for performance evaluation purposes intended, are only placed on the market or put into operation in Germany if they are provided with a CE mark . (The paragraphs refer to the German MPG.)

Medical devices may only be provided with a CE mark if the basic requirements according to § 7 MPG, which are applicable taking into account their intended purpose, are fulfilled and a conformity assessment procedure prescribed for the respective medical device (in accordance with the statutory ordinance according to § 37 para. 1 MPG ) has been carried out ( Section 6 (2) MPG).

The basic requirements for active implantable medical devices are the requirements of Annex I of Directive 90/385 / EEC, for in vitro diagnostics the requirements of Annex I of Directive 98/79 / EC and for other medical devices the requirements of Annex I of the Directive 93/42 / EEC.

In the case of class I products, the manufacturer is responsible for carrying out the conformity assessment procedure and for creating technical documentation including a risk management file for each product and keeping it available for inspection by the authorities. According to the report of the EU Commission of July 2, 2003, the national authorities are increasingly inspecting manufacturers who are not monitored by a notified body.

The certification by a state notified body must in Class IIa, IIb and III, and Is and Im (Class I products, which are placed in a sterile condition in the market or a measurement function have) are carried out in addition to the assessment by the manufacturer. The CE marking is then supplemented by a four-digit number. The manufacturer remains responsible for the product.

Manufacturer within the meaning of the Medical Devices Act is whoever places the product on the market for the first time within the EEA under their own name, regardless of who produces the product.

Medical device administrative regulation

On May 24, 2012, the federal government issued the General Administrative Regulation for the Implementation of the Medical Devices Act (Medical Devices Implementation Regulation - MPGVwV), which came into force on January 1, 2013.

The administrative regulation is addressed to the federal states and serves within the authorities to standardize the market surveillance of medical devices in Germany. The new coordination office of the federal states is the central office of the federal states for health protection for pharmaceuticals and medical devices (ZLG), based in Bonn.

The authorities are now increasingly carrying out unannounced audits at manufacturers and operators and checking whether the requirements for placing the medical devices on the market and putting them into operation are (continued) met. Section 1 (1) sentence 2 MPGVwV also obliges the states to monitor compliance with the requirements of the Therapeutic Products Advertising Act (HWG).

Manufacturing process

The manufacture of medical devices is subject to validation. This means that all manufactured parts of a batch have been checked for the properties guaranteed to the customer (product test; e.g. type test). Alternatively, the production process is validated. As a rule (for products of classes IIa, IIb and III) this is done in a certified quality management system in accordance with the DIN EN ISO 13485 standard (system test; e.g. complete QM system). Combinations of product and system tests are also possible.

Technical documentation for medical devices

There are special requirements for the documentation of a medical product due to laws and quality management.

Market figures in the EU including Switzerland and Norway

The market volume for medical devices in the EU including Switzerland and Norway is estimated at 95 billion euros for 2009. Around 4 billion euros of this will be used to develop new medical products. About 575,000 jobs are involved in the medical device industry. About 25,000 companies belong to the medical device industry, almost 95% of them small and medium-sized companies. The overall balance for the trade in medical products is positive, in 2012 it was 15.5 billion euros, which means an increase of more than double since 2006. According to the European Patent Office (EPA), the number of successful patents in the field of medical devices exceeded all other technical areas with 10,412 in 2012 . Worldwide, Germany ranks second behind the USA for medical device innovations.

Approval of medical devices in the EU and USA

Market access procedures in Europe

In order for a medical device to be marketed in the EU, directives 93/42 / EEC on medical devices, 90/385 / EEC on active implantable medical devices and 98/79 / EC on in vitro diagnostics (IVD) must be observed . The manufacturer is responsible for this. He must provide his products with a CE mark so that they can be marketed. Thereby he declares the conformity of the product with the corresponding legal requirements. The manufacturer must first determine the applicable guideline based on the intended purpose and mode of operation, then the risk class, according to which the conformity assessment procedure, among other things, is based. The "Basic Requirements" are used to evaluate a medical product and take into account the safety as well as the technical and medical performance of a medical product, particularly in accordance with the intended purpose and risk class. As part of the risk management system, a risk analysis must be carried out for all medical devices and, depending on the risk potential of the products, the conformity assessment procedure. The conformity assessment carried out by the manufacturer is checked by an independent testing and certification body (= notified body) and its correctness is confirmed according to uniform assessment standards. The higher the risk potential of the respective medical device, the higher the scope of the external external control. The notified body checks the medical devices, the manufacturing process of the products and / or the product documentation for compliance with the requirements of the relevant EC directives. If it determines that the manufacturer has complied with the relevant EC directives, it issues a directive approval and the manufacturer can affix the CE mark to the product.

US market access procedures

In the USA, the Center for Devices and Radiological Health (CDRH) within the FDA is responsible for the market approval of medical technology products. The basis for the work is the Medical Devices Regulation Act (1976). This law defines three risk categories for medical devices: Class I - low risk; Class II - moderate risk; Class III: high risk.

There are two different procedures for approval:

"Premarket Notification" (510k procedure)

For some medical technology products with a low to medium risk for the patient (classes I and II), the equivalence with a device or product already on the American market must be proven. This procedure is not a product approval, but a product release. For many Class I products and some Class II products, registration with the FDA is sufficient. In some cases, independent third parties are involved in this process and carry out an appropriate assessment. The ultimate decision rests with the FDA.

"Premarket Approval" (PMA)

Devices that pose a potentially high risk for the patient (Class III) are subject to official approval, namely the “Premarket Approval” (PMA). In this procedure, the safety (which must be verified for all product classes) and the effectiveness must be proven by clinical studies. However, this process is only used for around 1 percent of all products.

Ensuring the packaging, transport and storage stability of medical devices

Aspects such as correct packaging, transport and storage influence the quality of medical devices.

Packaging stability

A medical device should be packed in such a way that contamination by microorganisms can be excluded. When deciding on the right packaging, the nature of the medical products to be packaged, the requirements of the user, structural conditions and the transport logistics are taken into account. After the packaging process, the packaging should be checked for cleanliness and intactness. User-friendliness and security aspects must also be taken into account. Aspects such as B. simple filling, germ-tight sealing, suitability for the intended sterilization process, ensuring the function and sterility of the medical device through to use, possibility of aseptic removal of the contents, puncture resistance, transport to the place of use, labeling of the packaging or the contents and simple Handling of the packaging is crucial for the selection of the packaging. The information provided by the manufacturer must be taken into account on the packaging.

Transport stability

The medical device must not be damaged during transport. If there is a risk of contamination, the medical devices should be transported in protective packaging. The protective packaging is used for protection during transport and storage. If the protective packaging is opened, it must be closed again immediately after removal. Before opening the protective packaging, it should be ensured that the packaging is free of dust.

Storage stability

The storage stability of medical devices depends on criteria such as B. external influences, type of storage, type of transport and content of the packaging dependent. These conditions must be checked in relation to the products to be stored. The permissible storage period usually results from the manufacturer's information or is determined in writing by those responsible for hygiene. It should be noted that the specified storage period is only valid if stored properly and professionally.

Medical devices must be stored dry and dust-free and before

  • direct sunlight and UV radiation
  • damage
  • mechanical and chemical influences
  • Temperature fluctuations (maximum 20 K / day)
  • vermin

to be protected. The prescribed storage period is intended to minimize the risk of contamination during transport and opening.

Steps to the CE mark

  1. Determining the intended purpose
    Here, the medical purpose of the medical device must be observed. Intended patients, diagnoses or body parts must be determined. The physical principle of the medical device must be specified and the intended users and the usage environment.
  2. Allocation of the directives
    There are various EU directives that are applicable, for example the medical device directive MDD, in-vitro diagnostics directive IVDD or the active implantable medical device directive AIMD
  3. Allocation in classes
    The MDD (Medical Device Directive) divides medical devices into four classes (I, IIa, IIb and III).
    • Class I: There is a low risk in use
    • Class IIa: There is a medium risk in use
    • Class IIb: There is an increased risk when using it
    • Class III / active implants: If there is a high risk during use,
      the requirements for active implantable medical devices correspond to those made for class III products of Directive 93/42 / EEC due to their hazard potential.
  4. Selecting the conformity assessment procedure
    A suitable conformity assessment procedure depends on the class of the product.
    Appendix VII (EC declaration of conformity) -> CE marking without a notified body.
    A QM system is required for medical devices that contain or are software.
  5. Classifying a QM system Classifying
    a QM system takes a few weeks, saves months of time and improves product management.
  6. Product development Confirm
    with the QM system developed in-house, from which the technical documentation is created.
  7. Declaration of conformity
    a. Obtain a known place from the classes
    b. Then attach the CE mark

See also


  • Armin Gärtner: Medical device safety. Volume 1: Medical Device Legislation and Regulations. TÜV Media, 2008, ISBN 978-3-8249-1146-2 .
  • Armin Gärtner: Medical device safety. Volume 2: Electrical Safety in Medical Technology. TÜV Media, 2008, ISBN 978-3-8249-1164-6 .
  • Johann Harer: Requirements for medical devices: Practical guidelines for manufacturers and suppliers. Munich: Hanser, 2014 (2nd edition) ISBN 3-446-44041-0 .

Web links

European Union:





  1. The demarcation to pharmaceuticals was specified in Article 11 of the Second Act to Change Pharmaceutical Law and Other Provisions ( Federal Law Gazette 2012 I p. 2192, 2223 ) by wording Section 2 (5) No. 1 MPG as follows: “[…] the decision whether a product is a medicinal product or a medical product is made taking into account the main mode of action of the product, unless it is a medicinal product within the meaning of Section 2 (1) number 2 letter b of the Medicines Act, "
  2. WHO Global Health Expenditure Database, Eurostat, Eucomed calculations based on the data obtained from National Associations of 15 countries for the latest year available. Countries with (partially) provided data: Belgium, Czech Republic, Denmark, France, Germany, Greece, Ireland, Italy, Netherlands, Poland, Portugal, Spain, Sweden, UK, Switzerland. Medical technology includes in-vitro diagnostics. Europe refers to EU + Norway, Switzerland.
  3. a b Eucomed calculations based on the data obtained from National Associations of 15 countries for the latest year available. Countries with (partially) provided data: Belgium, Czech Republic, Denmark, France, Germany, Greece, Ireland, Italy, Netherlands, Poland, Portugal, Spain, Sweden, UK, Switzerland.Medical technology including in-vitro diagnostics. Europe refers to EU + Norway, Switzerland
  4. Espicom, Eucomed calculations. Manufacturer prices. Medical device excluding in-vitro diagnostics. Europe refers to EU + Norway, Switzerland.

Individual evidence

  1. Bienkowska welcomes the adoption of new EU rules on medical devices. Press office of the European Commission Germany, April 5, 2017, accessed on January 17, 2019 (press release).
  2. Market access regulations for medical devices compared to pharmaceuticals ( memento of the original from January 31, 2012 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. (PDF; 66 kB) BMG poster @1@ 2Template: Webachiv / IABot /
  3. Directive 90/385 / EEC
  4. Directive 93/42 / EEC
  5. Directive 98/79 / EC
  6. Regulation (EU) 2017/745
  7. Regulation (EC) No. 1223/2009
  8. § 2 Paragraph 3 No. 7 AMG.
  9. § 4 Paragraph 1 No. 6 MPG.
  10. MEDDEV guidelines
  11. Part1 ( Memento of the original from August 30, 2006 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. and Part2 ( Memento of the original from August 30, 2006 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. (PDF). @1@ 2Template: Webachiv / IABot / @1@ 2Template: Webachiv / IABot /
  12. Federal Institute for Drugs and Medical Devices: Medical Devices - Delimitation / Classification. 2013 ; accessed on January 9, 2019
  13. Error: Invalid time specification Council Directive 93/42 / EEC of June 14, 1993 on medical devices in the consolidated version of November . Last changed on September 5, 2007; P. 8; accessed on January 10, 2019
  14. ^ Medical devices - European Commission. In: Retrieved May 11, 2016 . -
  15. Andreas Schwarzkopf: Practical knowledge for hygiene officers. W. Kohlhammer, Stuttgart 2016, ISBN 978-3-17-028660-3 , p. 144.
  16. Flowchart of the DGSV for the classification of medical devices 2013. Revised version, created on the basis of the KRInKO / BfArm recommendation on the hygiene requirements for the reprocessing of medical devices, Federal Health Gazette 2012; 55: 1244-1310.
  17. a b Gerhard Hegendörfer: The current status of the reform of the EU medical device law. In: Medicine Products Law. 6, 2013, pp. 181-188.
  18. BAnz AT May 24, 2012 B2 .
  19. a b c d e Eucomed: 2009 editions for EU-27, Norway and Switzerland ( Memento of the original from July 14, 2014 in the Internet Archive ) Info: The @1@ 2Template: Webachiv / IABot / archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. . Accessed June 12, 2014.
  20. BVMed : Germany as an innovation location for medical technology. In: Medicine Products Law. 6, 2013, p. III.
  21. accessed on May 3, 2016.
  22. Archived copy ( memento of the original from June 3, 2016 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. accessed on May 4, 2016. @1@ 2Template: Webachiv / IABot /
  23. accessed on May 4, 2016.
  24. accessed on May 6, 2016.
  25.ösungen-33241955 accessed on May 3, 2016.
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