1
Published 2007
Bundesministerium für Bildung und Forschung

2
Published 2004
OECD Publishing

3
by Keeley, Brian
Published 2008
OECD Publishing

4
Published 2012
OECD Publishing

5
Published 2013
OECD Publishing

6
Published 2013
German Youth Institute

7
by Sowa, Frank
Published 2017
Nomos Verlagsgesellschaft mbH & Co. KG

8
by Dopheide, Christian
Published 2017
Nomos Verlagsgesellschaft mbH & Co. KG

9
by Altmeppen, Klaus-Dieter
Published 2017
Nomos Verlagsgesellschaft mbH & Co. KG