Summa.
Library
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New Testament
Theology
Summa Theologica · St. Thomas Aquinas
City of God · St. Augustine
Church Doctrine
Catechism of the Catholic Church
Code of Canon Law (1983)
General Instruction of the Roman Missal
Papal Encyclicals
Humanae Vitae
Laudato Si'
Veritatis Splendor
Rerum Novarum
Fides et Ratio
Deus Caritas Est
Spe Salvi
Evangelii Gaudium
Pacem in Terris
Quadragesimo Anno
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Dei Verbum
Lumen Gentium
Council of Trent: Canons and Decrees
Philosophy
Confessions · St. Augustine