TY  - BOOK
AU  - Dirk Leuffen, Berthold Rittberger, Frank Schimmelfennig
TI  - Integration and Differentiation in the European Union
SN  - 9783030766771
PB  - Springer
UR  - https://link.springer.com/openurl?genre=book&isbn=978-3-030-76677-1
ER  -