Stephen Schanuel

Stephen H. Schanuel (1933—2014) was an American mathematician working in the fields of abstract algebra and category theory, number theory, and measure theory.
Life.
While he was a graduate student at University of Chicago, he discovered Schanuel's lemma, an essential lemma in homological algebra. Schanuel received his Ph.D. in mathematics from Columbia University in 1963, under the supervision of Serge Lang.
Work.
Shortly thereafter he stated a conjecture in the field of transcendental number theory, which remains an important open problem to this day. Schanuel was a professor emeritus of mathematics at University at Buffalo.