Richard S. Westfall  is best known for his biography of a mathematician who was a key figure in what?
Richard S. Westfall Richard S. Westfall (April 22, 1924 – August 21, 1996) was an American academic, biographer and historian of science. He is best known for his biography of Isaac Newton and his work on the scientific revolution of the 17th century.
Émile Léonard Mathieu Émile Léonard Mathieu (] ; 15 May 1835, Metz – 19 October 1890, Nancy) was a French mathematician. He is most famous for his work in group theory and mathematical physics. He has given his name to the Mathieu functions, Mathieu groups and Mathieu transformation. He authored a treatise of mathematical physics in 6 volumes.