Blech, Benjamin; Doliner, Roy.. The Sistene Secrets. New York, NY: HarperCollins Publishers, 2008, p. 106. ISBN 978-0-06-146904-6. The term 'terrible' was first applied by Julius himself to Michaelangelo, and only later to the Pope by others: Pastor 1902, VI, pp. 214–5
Pastor 1902, VI, p. 209, citing the original sources and scholarship. Philip Hughes agrees: Hughes, Philip. «Chapter V: 'Facilis Descensus ...' 1471–1517: A Papacy of Princes». A: History of the Church: Volume 3: The Revolt Against the Church: Aquinas to Luther. revised. Londres: Sheed & Ward, 1979, p. 415. ISBN 978-0-7220-7983-6.
In the 17th and 18th centuries they were used for accommodations during papal conclaves. Paul Maria Baumgarten, in: The Catholic Encyclopedia. Volume Fifteen. Nova York: Encyclopedia Press, 1913, p. 284.
Jokinen, Anniina. «Pope Julius II», 15-03-2003. [Consulta: 7 octubre 2013].
newadvent.org
Indulgences (which remit the temporal effects of sins that have already been forgiven) involve the person receiving the indulgence doing some sort of good work, like donating to a charitable cause. «Indulgences». New York: Robert Appleton Company. [Consulta: 26 maig 2020].
Ott, Michael. «Pope Julius II». A: The Catholic Encyclopedia. 8. Nova York: Robert Appleton Co., 1910.From New Advent website