J. D. North, "The Western Calendar: 'Intolerabilis, Horribilis, et Derisibilis': Four Centuries of Discontent." In: G. V. Coyne, M. A. Hoskin, O. Pedersen, Gregorian Reform of the Calendar: Proceedings of the Vatican conference to commemorate its 400th anniversary. Specola Vaticana, Città del Vaticano, 1983 (in interrete); p. 78
A. Ziggelaar: The Papal Bull of 1582 Promulgating a Reform of the Calendar. In: G. V. Coyne, M. A. Hoskin, O. Pedersen, Gregorian Reform of the Calendar: Proceedings of the Vatican conference to commemorate its 400th anniversary. Specola Vaticana, Città del Vaticano, 1983 (in interrete); p. 223
