Catechism of the Catholic Church §1513 — excerpt
The Apostolic Constitution Sacram unctionem infirmorum, following upon the Second Vatican Council, established that henceforth, in the Roman Rite, the following be observed:
This translation is under copyright, so only the cited words are quoted here. Follow the link for the full text. Translation: English translation of the Catechism of the Catholic Church, 2nd ed. (Libreria Editrice Vaticana), as posted at vatican.va.
Also cites: Paul VI, apostolic constitution, Sacram unctionem infirmorum, November 30, 1972 · SC 73 · CIC, Can. 847 # 1