Code of Canon Law http://www.vatican.va/archive/ENG1104/_INDEX.HTM

GIRM (General Instruction of the Romal Missal http://www.vatican.va/roman_curia/congregations/ccdds/documents/rc_con_ccdds_doc_20030317_ordinamento-messale_en.html

Catechism of the Catholic Church http://www.vatican.va/archive/ENG0015/_INDEX.HTM

EWTN presents the teachings of the Catholic Church in an easy to use format https://ewtn.com/faith/teachings/index.asp

St Thomas Aquinas’ Summa Theologica http://www.sacred-texts.com/chr/aquinas/summa/