Who comprises the European Union's "inner" core and who is on the outside?

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Clarification of Question by hugscub-ga on 22 Dec 2005 06:37 PST

of the countries who are current members

The European Union has 25 member countries, of these the inner core
may be either the 15 members prior to the acceptance of 10 new members
in 2004, or it may be those members who now use the "Euro" as a common
currency.  There are also countries on the "waiting list", but these
are not considered part of the EU.
The Wikipedia site should give you all the additional details you need.
For a list of when countries became members, scroll down about 1/4 of the way:
http://en.wikipedia.org/wiki/European_Union