Doctor of Physico-Mathematical Science since 1935. Professor 1933, Rector since 1951, Moscow University. Full member, USSR Academy of Science, since 1946.
Senior associate, Mathematical Institute, USSR Academy of Science, since 1943. Presidium member, USSR Academy of Science, since 1953. Member, Editor and Publ.
Council, USSR Academy of Science, since 1955. Chief Editor, journal “Matematichesky sbornik” (Mathematical Symposium), since 1950. Member, Soviet Committee the Defense of Peace, since 1955.
1930-1933 Assistant, then lecturer, Moscow University. 1930-1941 Professor, and Head, Chair of Higher Mathematics, Machine-Building Evening Institute, Popular Commissariat of Heavy Machine-Building. 1940-1944 Dean, Mech. and Mathematics Faculty, Moscow University.
1947-1949 Deputy Director, Mathematical Institute, USSR Academy of Science. 1949-1951 Academy Secretary,Department of Physico-Mathematical Science, USSR Academy of Science. Specialist in theory of partial differential equations, probability theory and qualitative theory of ordinary differential equations.