Biography of Carl Ludwig Siegel Carl Ludwig Siegel was born on December 31, 1896 in Berlin. He studied mathematics and astronomy in Berlin and Göttingen and held chairs at the Universities of Frankfurt and Göttingen before moving to the Institute for Advanced Study in Princeton in 1940. He returned to Göttingen in 1951 and died there in 1981. Siegel was one of the leading mathematicians of the twentieth century, whose work, noted for its depth as well as breadth, ranged over many different fields such as number theory from the analytic, algebraic and geometrical points of view, automorphic functions of several complex variables, symplectic geometry, celestial mechanics. Biography of Jürgen Moser Jürgen Moser was born on July 4, 1928 in Königsberg, then Germany. After the war he studied in Göttingen, where he received his doctoral degree in 1952 and subsequently was assistant to C.L. Siegel. In 1955 he emigrated to the USA. He held positions a M.I.T., Cambridge and primarily at the Courant Institute of Mathematical Sciences in New York; from 1967 to 1970 he was Director of this institute. In 1980 he moved to the ETH in Zürich where he now is Director of the mathematical Research Institute. Moser has worked in various areas of analysis. Besides celestial mechanics and KAM theory he contributed to spectral theory, partial differential equations and complex analysis.