Felix Klein

Christian Felix Klein (25 April 1849 – 22 June 1925) was a German mathematician and mathematics educator, known for his work in group theory, complex analysis, non-Euclidean geometry, and on the connections between geometry and group theory. His 1872 Erlangen Program, classifying geometries by their underlying symmetry groups, was a hugely influential synthesis of much of the mathematics of the day.

Abbé Félix Klein (12. July 1862 Château-Chinon – December 1953 Gargenville) was a French priest, theologian and author, who taught at the Institut Catholique de Paris. In the US, he is known as the author of the introduction of Comptesse de Ravilliax's French translation of Walter Elliott's Life of Father Hecker (1896), which started the Americanism controversy. Klein was made Chevalier of Legion of Honour in 1952. Many of Abbé Klein's personal papers are kept in the University of Notre Dame Archives.