Pavel Urysohn and Leonid Levin are not both known for the same type of work.
Pavel Samuilovich Urysohn (   ) (February 3, 1898  August 17, 1924) was a Soviet mathematician of Jewish origin who is best known for his contributions in dimension theory, and for developing Urysohn's Metrization Theorem and Urysohn's Lemma, both of which are fundamental results in topology. 
Leonid Anatolievich Levin ( ; Russian:    ; Ukrainian:    ; born November 2, 1948) is a Soviet-American computer scientist. 
