""...The present map, on the other hand, takes not language, but national conciousness as the only satisfactory criterion of nationality..."" - The original, detailed explanation from the publisher of the map is exposed here. Important factor: the map shows the population, as it was before the 1923-1930 population exchange processs, and before migrations caused by the Greek civil war. The map recognizes the "Macedonian Slavs" nationality, as a separate one, non-Bulgarian.