Subject: Epistolae
Author of work: Gregorius I
Title: Registrum
Subject: Theology
Title: Theology
Subject: Canon Law
Title: Comment. on canon law
Subject: Theology
Author of work: Aegidius Romanus
Title: Expositio secundi libri Sententiarum Petri Lombardi
Subject: Canon Law
Author of work: Gregorius IX
Title: Decretales
Subject: Liturgy
Title: Breviarium
Subject: Theology
Author of work: Thomas Aquinas
Title: Summa theologiae
Subject: Liturgy
Title: Pontificale
Subject: Liturgy
Title: Missale
Subject: Civil Law
Author of work: Justinianus
Title: Digestum novum