Oskar Halecki (1891 in Vienna - 1973 near New York) Polish historian, social and Catholic activist. 1891 (MDCCCXCI) was a common year starting on Thursday (see link for calendar). ... Vienna (German: Wien [viːn]; Slovenian: Dunaj, Croatian and Serbian: Beč Romanian: Viena, Hungarian: Bécs, Czech: Vídeň, Slovak: Viedeň, Romany Vidnya;) Vienna is the capital of Austria, and also one of the nine States of Austria. ... 1973 (MCMLXXIII) was a common year starting on Monday (the link is to a full 1973 calendar). ... Official language(s) None, English de facto Capital Albany Largest city New York City Area  - Total  - Width  - Length  - % water  - Latitude  - Longitude Ranked 27th 141,205 km² 455 km 530 km 13. ...

As a historian, Halecki was an expert on medieval history of Poland and Lithuania, and history of Byzantine Empire. The Middle Ages formed the middle period in a traditional schematic division of European history into three ages: the classical civilization of Antiquity, the Middle Ages, and modern times, beginning with the Renaissance. ... Byzantine Empire (Greek: ) is the term conventionally used since the 19th century to describe the Greek-speaking Roman Empire during the Middle Ages, centered at its capital in Constantinople. ...

Halecki was one of the founders of Polish Institute of Arts and Sciences of America in 1942, its first Executive Director and later its President (1952-1964). He was an expert of the Polish delegation at the Peace Conference in Paris (1918-1919); member of League of Nations Secretariate (1921-1924); member of Warsaw Scientific Society since 1927; chairman of Polish Heraldic Society (1930-1939); member of the Polish Academy of Arts and Sciences in Kraków (1944–1961). Professor of Warsaw University (1919-1939), member of Polish Academy of Learning; professor of Fordham University, New York, Columbia University; visiting professor in Rome, Montreal and Berkeley. Warsaw University (Polish Uniwersytet Warszawski) - the biggest and one of the most prestigious universities in Poland. ... The Polish Academy of Skills (Polish: Polska Akademia Umiejętności, PAU), till 1919 just The Academy of Skills (Akademia Umiejętności, AU) founded in 1872 in Kraków as continuation of the Kraków Scientific Society (Towarzystwo Naukowe Krakowskie, est. ... Fordham University is a prestigious co-educational private university in New York City. ... Columbia University is a private university in the Morningside Heights neighborhood of Manhattan, New York City and a member of the Ivy League. ...