Columbia subject headings:
Harvard subject headings:
History, Ancient--Mathematical models.
History, Ancient--Miscellanea.
Middle Ages--Chronology
Middle Ages--Miscellanea.
Russia--History--Chronology.
Russia--History--Mathematical models.
Princeton subject headings:
History, Ancient--Mathematical models.
Middle Ages--History--Chronology.
Russia--History--Chronology.
Russia--History--Mathematical models.