There he was given an honorary Master of Arts degree. The following year he joined the faculty of McGill University where the endowments of Peter Redpath financed a professorship. He was at McGill for a decade with leaves of absence to the Institute for Advanced Study (1955/6) and California Institute of Technology (1958/9). There he was using computers to advance number theory. In 1959 Zassenhaus began teaching at University of Notre Dame and became director of its computing center in 1964. Zassenhaus was a Mershon visiting professor at Ohio State University in the fall of 1963. In 1965 he came to Ohio State permanently. The mathematics department was led by Arnold Ross; Zassenhaus found a home there until his retirement in 1982. Nonetheless, he continued to take leaves of absence for visits to Göttingen (summer 1967), Heidelberg (summer 1969), UCLA (fall 1970), Warwick (fall 1972), CIT (1974/75), U Montreal (1977/78), Saarbrücken (1979/80). He served as editor in chief of the Journal of Number Theory from its first issue in 1967. He won a Lester R. Ford Award in 1968. Hans Zassenhaus died in Columbus, Ohio on November 21, 1991. His doctoral students include Joachim Lambek. Important publications Hans Julius Zassenhaus (1937), Lehrbuch der Gruppentheorie ("Textbook of group theory"), 2nd edition (1960),The theory of groups. A famous group theory book based on a course by Emil Artin given at the University of Hamburg during winter semester 1933 and summer semester 1934. Zassenhaus showed that there are just seven near-fields that are not division rings or Dickson near-fields in Abhandlungen aus dem Mathematischen Seminar der Universität Hamburg 11, pp 187–220. In 1977 Academic Press published Number Theory and Algebra, a collection of papers dedicated to Henry B. Mann, Arnold E. Ross, and Olga Taussky-Todd, edited by Zassenhaus (). It included "A Theorem on Cyclic Algebras" by Zassenhaus. Cambridge University Press published Algorithmic Algebraic Number Theory written by Zassenhaus and M. Pohst in 1989 (). A second edition appeared in 1993. . The paper that introduced the Cantor–Zassenhaus algorithm for factoring polynomials. See also Pfister's sixteen-square identity Z-group Zassenhaus dual expansion Zassenhaus algorithm Zassenhaus formula Zassenhaus group Zassenhaus lemma Zassenhaus neghbourhood Berlekamp–Zassenhaus algorithm Cantor–Zassenhaus algorithm Schur–Zassenhaus theorem References M. Pohst (1994) "Hans Zassenhaus", Journal of Number Theory 47:1–19. External links Biography from the Ohio State University 1912 births 1991 deaths 20th-century German mathematicians Group theorists University of Notre Dame faculty Ohio State University