Columbia subject headings:
Charlemagne, Emperor, 742-814--Congresses.
Civilization, Medieval--Congresses.
Mathematics--History--Congresses.
Science, Medieval--History--Congresses.
Science--Europe--History--Congresses.
Harvard subject headings:
Charlemagne, Emperor, 742-814--Congresses.
Civilization, Medieval--Congresses
Europe--Civilization--Congresses.
Mathematics--History--Congresses
Science, Medieval--History--Congresses.
Science--Europe--History--Congresses.
Princeton subject headings:
Charlemagne, Emperor, 742-814--Influence--Congresses.
Europe--Civilization--Congresses.