During the 1930s Klein also found time to attend conferences, not the least of which included the 1938 Warsaw Conference where he spoke on (almost) non-Abelian gauge theories.
Sa panahon ng 1930s Klein din natagpuan ang oras na dumalo sa Conferences, hindi man lamang ng mga kasama na ang 1,938 Warsaw Conference kung saan siya nagsalita sa (halos) non-Abelian sukatin theories.