Blackboards; Einstein, Albert, 1879-1955; Sitter, Willem de
Dr. Willem de Sitter looks on as Albert Einstein points up. A blackboard with computations is mounted behind them. "for my young friend Kathleen Drucker from de Sitter's daughter. Theodora Smit" is written on the back of the photograph.
Autographs; Books; Drucker, Peter F. (Peter Ferdinand), 1909-2005;
Drucker sits on a rolling chair in front of a table and signs a book. A man with a book in his hand bends towards him and shows him a piece of paper. Another man holds a book and piece of paper in his hand.