Columbia subject headings:
Catholic Church--Liturgy--History--Middle Ages, 600-1500.
Catholic Church. Pontifical (Romano-Germanic pontifical)
Penance--History of doctrines--Middle Ages, 600-1500.
Harvard subject headings:
Catholic Church. Pontificale Romano-Germanicum.
Penance--History of doctrines--Early church, ca. 30-600.
Penance--History of doctrines--Middle Ages, 600-1500.
Penitentials.
Pontificals.
Princeton subject headings: