Graduate Theology

Selected and edited by Henry Bettenson and Chris Maunder.
4th edition. Oxford: Oxford University Press, 2011.
A standard collection of excerpts from the primary sources most frequently referred to in theological study: from antiquity to the modern period and including both Catholic and Protestant documents.
For print version locations, see the UofT Library Catalogue.

Washington, DC: Catholic University of America Press, 1947–present.
139 volumes in print. 117 volumes available online.
For print version locations, see the UofT Library Catalogue.

Paulist, 1946–present. 75 volumes and growing.

Thomas Aquinas.
London: Blackfriars, 1964-1976. 61 volumes.
Saint Thomas' Summa theologiae is the principal doctrinal synthesis of Catholic theology. The 1964 edition by the English Dominicans includes the Latin text and an English-language translation on facing pages; each volume includes a subject index and a useful glossary of theological terms.
Some volumes of the 1964 edition are available online on the Internet Archive, a trusted source, but one for which it is necessary to create a free account and login:
volume 1 (1a 1-13),
volume 7 (1a 33-43),
volume 14 (1a2ae 103-109),
volume 15 (1a 2ae 110-119),
volume 27 (1a2ae 86-89),
volume 31 (2a2ae 1-7),
volume 33 (2a2ae 17-22),
volume 38 (2a 2ae 63-79),
volume 40 (2a2ae 92-100),
volume 41 (2a 2ae 101-122),
volume 44 (2a 2ae 155-170),
volume 45 (2a 2ae 171-178),
volume 47 (2a 2ae 183-189),
volume 48 (3a 1-6),
volume 49 (3a 7-15),
volume 51 (3a 27-30),
volume 52 (3a 31-37),
volume 51 (3a 38-45),
volume 56 (3a 60-65),
volume 59 (3a 79-83).
There are several other English translations available online including the 1920 version by the English Dominicans and a contemporary version by Alfred J. Freddoso.