Philologist
His books include The Ukrainian Language and Its Dialects, in Ukrainian, (1937; 5th revised ed. 1978), a German-language textbook of Ukrainian (1940; 4th ed. 1964), A Modern Ukrainian Grammar for English speakers (1949; reprinted seven times), and a pioneering but incomplete English-language Etymological Dictionary of the Ukrainian Language (2 volumes in 22 fascicles, 1962–1982). He also produced several smaller Ukrainian language books on the origins of various Ukrainian placenames including "Galicia", "Volhynia", and, in most detail, "Ukraine". As well, he wrote on Canadian, especially Manitoban, placenames of Ukrainian origin.
During the Second World War, he published a short Ukrainian-German Dictionary which quickly went through four editions: (1940; 1941; 1942; and 1943). Together with Zenon Kuzelia, he also published a much larger Ukrainian-German Dictionary (1943; reprinted 1983) which was a pioneering effort in its day. (It contained over 100,000 words.)
Read more about this topic: Jaroslav Rudnyckyj