Columbia subject headings:
Harvard subject headings:
Byzantine Empire--History--Constantine VII Porphyrogenitus, 913-959.
Nikolaos I, Mystikos, Saint, Patriarch of Constantinople, 852-925.
Simeon I, King of Bulgaria, 864 or 865-927
Princeton subject headings:
Nikolaos I, Mystikos, Saint, Patriarch of Constantinople, 852-925.
Simeon I, King of Bulgaria, 864 or 865-927.