 Afterwards he concentrated on historical research.He researched linguistics (particularly Slavic languages), ethnography of the Central and Eastern European lands, and history of literature.He would serve as the director of two institutes ("Instytut Badania Najnowszej Historii Polski" (Institute of Studies of Modern Polish History) in the 1920s and "Instytut Badań Narodowościowych" (Institute of Nationality Studies) in the 1930s) and editor of the journal "Niepodległośc".