Thurston, Herbert (July–December 1904). "The Origin of the Scapular – A Criticism". The Irish Ecclesiastical Record. 16: 59–75. Retrieved Jan 31, 2025. Thurston demonstrates that the Swanington letter was not authentic, and that the papal bull that was the basis of the "Sabbatine privilege" was also forged. The article explores Carmelite history and the evolution of the scapular devotion.
1912 Catholic Encyclopedia. Sabbatine Privilege – "The Bull [of the Holy Roman General Inquisition 20 January 1613, clarifying what is permissible for the Carmelites to preach regarding the Brown Scapular"] forbids the painting of pictures representing, in accordance with the wording of the Bull, the Mother of God descending into purgatory (cum descensione beatae Virginis ad animas in Purgatorio liberandas)."