What profession has both Ivan Fesenko and Mark Krein held?
Mark Krein Mark Grigorievich Krein (Ukrainian: Марко Григорович Крейн , Russian: Марк Григо́рьевич Крейн ; 3 April 1907 – 17 October 1989) was a Soviet Jewish mathematician, one of the major figures of the Soviet school of functional analysis. He is known for works in operator theory (in close connection with concrete problems coming from mathematical physics), the problem of moments, classical analysis and representation theory.
Mark Morris (choreographer) Mark William Morris (born August 29, 1956) is an American dancer, choreographer and director whose work is acclaimed for its craftsmanship, ingenuity, humor, and at times eclectic musical accompaniments. Morris is popular among dance aficionados, the music world, as well as mainstream audiences.