Columbia subject headings:
Léonin, active 12th century.
Music--France--Paris--500-1400--History and criticism.
Pérotin, -1238?
Harvard subject headings:
Léonin, active 12th century.
Music--France--Paris--500-1400.
Organa--History and criticism
Pérotin, -1238?
Princeton subject headings:
Léonin, active 12th century.
Music--France--Paris--500-1400--History and criticism.
Pérotin, -1238?