The pictures of Einstein and Gauss have been found on the internet and don't seem to be protected by any copyright.
The picture of Savant Cosinus is used with Permission from The Paris Pages. It has been download from the site http://www.paris.org/Expos/Cosinus/. This picture has been scanned by Thomas Netter from the book L'idée fixe du Savant Cosinus by Christophe published by ARMAND COLIN.
For any comments and complaints please write to h03@lpt.ens.fr