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Browne, P. W. (4 May 2018). "The Pactum Callixtinum: An Innovation in Papal Diplomacy". The Catholic Historical Review. 8 (2): 180–190. JSTOR25011853.
Kuhn, Gary G. (1985). "Church and State Conflict in El Salvador as a Cause of the Central American War of 1863". Journal of Church and State. 27 (3): 460–461. doi:10.1093/jcs/27.3.455. JSTOR23916318.