Finno-Ugric languages
He spoke ca. 20 languages fluently. He studied not only spoken languages such as German, Finnish, Swedish, Russian but classical languages Latin and Old Greek, too. He translated Horace's Best Odes and Ammianus Marcellinus' "The Roman History" (Rerum Gestarum Libri) from Latin into Hungarian. He had a comprehensive knowledge of the Finno-Ugric languages, and he used this knowledge in his doctoral dissertation about the Hungarian possessive constructions such as "isten-adta" /god-given/ in Finno-Ugric languages in 1939. This work is the most detailed source of description of the prenominal relative clauses in Finno-Ugric languages, though he considered and analyzed this constructions as possessive constructions. He fought against the linguistic superstitions in Hungarian.