This Saint Thomas Aquinas selection comes from his Summa Theologica, PRIMA PARS, Second and Revised Edition, 1920; trans. by Fathers of the English Dominican Province. The William Paley selection is drawn from Natural Theology (1801).
The full Proslogium is available from The Medieval Sourcebook. The notes in the text are based on those of Paul Halsall, and the translation is David Burr’s. Special thanks to Gideon Rosen for the use of his commentary on Anselm’s argument.