In January he published the first details of his new approach, developed with physicists at the Heinrich-Heine University of Dusseldorf.

ECONOMIST: Case history

The university of Dusseldorf decided to look into Ms Schavan's 1980 doctoral thesis after an anonymous blogger raised questions about it.

BBC: German minister Annette Schavan quits over 'plagiarism'

The university of Dusseldorf has been looking into Ms Schavan's 1980 thesis for several months after an anonymous blogger raised questions about it.

BBC: German minister Annette Schavan denies plagiarism