More than 200 letters, many of them in German, written to Eric Riessner (1913-1996), a German-born mathematician. Correspondents include Reissner's father, Hans, a prominent German aeronatuical engineer whose avocation was mathematical physics; Bernhard Hermann Neumann, a German-born British-Australian mathematician who was a leading figure in group theory; William Prager, a German expert in the fields of vibrations, plasticity and the theory of structures; and many other prominent scientists as well as other friends of the Reissners.