Which Russian mathmatician contributed to number theory, Grigori Perelman or Ivan Fesenko?
Ivan Fesenko Ivan Fesenko (Russian: Иван Борисович Фесенко ; born 1962) is a mathematician working in number theory and other areas of modern mathematics.
Sergey Stechkin Sergey Borisovich Stechkin (Russian: Серге́й Бори́сович Сте́чкин ) (6 September 1920 – 22 November 1995) was a prominent Soviet mathematician who worked in theory of functions (especially in approximation theory) and number theory.