Calvarian presented information about researching flags, as to the ways to classify certainty. Calvarin's paper was entitled Doubts and Certainties in Vexillology.
Among primary sources for flags comes via written laws and ordinances, archives, photos, videos, and postal stamps. Secondary sources include vexillological work, dictionaries, reference books, press articles, and testimonials. Calvarian noted that written descriptions can be wildly interpreted.
Essentially many flag designs can be lost in the march of history, being real or not. But Calvarian established an efficient rubric that allows one to grade the source as to its reliability.