Series consists of personal and professional correspondence with leading scientists, mathematicians and education specialists from across Europe and North America. As Wittenberg did not maintain copies of his letters, for the most part the series only contains the incoming letters. The series includes correspondence with scholars such as Paul Bernays, Alexander Calandara, Tatiana Ehrenfest Afanasyeva, Ferdinand Gonseth, Ahron Katchalsky (Katzir), Thomas Kuhn, Imre Lakatos, Georges Polya, Michael Polanyi and many other colleagues and acquaintances. There are several files pertaining to Wittenberg’s involvement with councils, associations and other initiatives that aimed to promote mathematical and scientific education across Canada and North America. The series also contains materials of more personal nature pertaining to matters such as trips, children schools, post-Holocaust restitution claims, and involvement in Canadian Jewish community life.