| Members | ||
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Belgium | Member since 1999 |
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The Netherlands | Member since 1999 |
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Luxemburg | Member since 1999 |
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France | Member since 1999 |
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Germany | Member since 2001 |
 |
Ireland | Member since 2001 |
 |
United Kingdom | Member since 2002 |
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Poland | Member since 2004 |
 |
Austria | Member since 2004 |
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Romania | Member since 2007 |
| Portugal | Member since 2023 | |
 |
Hungary | Member since 2007 |
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Croatia | Member since 2015 |
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Spain | Member since 2019 |
| Observers | ||
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Czech Republic | Observer since 2010 |
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Slovenia | Observer since 2010 |