The general rule is that people that have been declared a saints, appear as authors without their title -- that is what I expect. However, a few have kept the St. in front of their name:
- St. Peter of Alcantara. Finding God through Meditation. Edited by Daniel Burke. Translated by Giles Willoughby. Revised edition. Navigating the Interior Life. Steubenville, OH: Emmaus Road Publishing, 2015.
- and 17 resources of St. Pius X which should be simply Pius X - note error is in the library not in the citation.