Moravia (Germ. Maehren) was part of the Austro-Hungarian Empire, i.e. "Austria" and people of any ethnic group would be "Austrian" by citizenship, so that would be correct for that time. Bohemia (Germ. Boehmen) was also part of the A-H Empire and both these became part of Czechoslovakia c. 1919. Yugoslavia was created, as said, from a group of Balkan Austro-Hungarian states - Serbia, Slovenia, Croatia, Bosnia which are now independent states as Yugoslavia no longer exists. If the person is to be traced, as said again, the most important thing is the language spoken at home, Serb? Croat?, Bosnian? with the religious denomination also being good for a clue. History is very important for Central Europe but sorting out the history is complex and ethnicity is often the best starting point.