Matthias Schulz (25 January 2010). "Schleifstein der Schande" (in German). Der Spiegel. Archived from the original on 2 February 2010. Retrieved 30 January 2010.
Matthias Schulz (25 January 2010). "Schleifstein der Schande" (in German). Der Spiegel. Archived from the original on 2 February 2010. Retrieved 30 January 2010.