Columbia subject headings:
Harvard subject headings:
Catholic Church--Liturgy--Texts.
Gregorian chants--History and criticism.
Offertories (Music)--Sources.
Prosulas (Music)--500-1400--Sources.
Tropes (Music)--Sources.
Princeton subject headings:
Catholic Church--Liturgy--Texts.
Gregorian chants--History and criticism.
Offertories (Music)--Sources.
Prosulas (Music)--500-1400--Sources.
Tropes (Music)--Sources.