His first post was at Brown University then, in 1945, he joined von Mises in Harvard. However his stay in Harvard was a short one and he then moved to Stanford where he spent the rest of his career.
Kanyang unang post ay sa Brown University at pagkatapos, sa 1945, siya sumali sa von Mises sa Harvard. Subalit sa kanyang manatili sa Harvard ay isang maikling isa at siya pagkatapos ay inilipat sa Stanford kung saan niya nagastos ang natitirang bahagi ng kanyang karera.