Gäbler, Bernd; Grimm, Imre (31 May 2010). "Ein Solo für zwei". Die Zeit (in German). Archived from the original on 7 October 2012. Retrieved 22 July 2012.
Gäbler, Bernd; Grimm, Imre (31 May 2010). "Ein Solo für zwei". Die Zeit (in German). Archived from the original on 7 October 2012. Retrieved 22 July 2012.