Ferdinand Gregorovius, History of Rome in the Middle Ages, Volume IV. 2 second edition, revised (London: George Bell, 1896), pp. 439-442. J. P. Adams, "Sede Vacante 1138 (Roman Obedience)," (California State University Northridge 2011); retrieved: 28 September 2021.
Johann Peter Kirsch (1910), "Liber Pontificalis."The Catholic Encyclopedia; Vol. 9 (New York: Robert Appleton Company); retrieved: 27 September 2021.
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Pandolfo of Pisa, Pandolfo Pisano, Pandulfus of Pisa, Pandulfus Pisanus, Pandulfus Aletrinus, Pandulphus Pisanus, Pandulphus Aletrinus. Pandulf was not from Pisa; this was an old confusion with the cardinal Pandulf of XII Apostolorum (c. 1140–1210), and with Pandolfo Masca. Anzoise, "Pandolfo da Alatri."
Zenker, p. 145. Brixius, pp. 48, 97. Cf. Anzoise, "Pandolfo da Alatri.": "He was probably a native of Alatri like his uncle Ugo, the cardinal presbyter of the XII Apostles (1116-1121/1122), but nothing is known of his life before he arrived in Rome following his uncle, perhaps already during the pontificate of Urban II, as hypothesized by Přerovský (Liber Pontificalis, 1978)."
Anzoise, "Pandolfo da Alatri.": "Pandolfo was then certainly present at the election of Gelasius II (24 January 1118), as evidenced by the detailed description he makes of the event in the biography of the pontiff."
Watterich II, p. 116. Anzoise, "Pandolfo da Alatri.", states that Pandulfus had left Benevento some time before, though without evidence.
Hüls, p. 151. He subscribes documents there from 8 August through October. In 1121, Hugo served as papal legate to arrange a peace between Roger of Sicily and William of Apulia; he died shortly thereafter: Watterich II, p. 116. Anzoise, "Pandolfo da Alatri.": "All’ultimo scorcio del 1121 o al 1122 dovrebbe datarsi la morte dello zio di Pandolfo, il cardinale Ugo dei XII Apostoli, evento ricordato con tristezza nella biografia di Callisto II."
Watterich II, pp. 157-158. Anzoise, "Pandolfo da Alatri.": "Ancora una volta, i ricchi particolari narrati nella biografia di Onorio II lasciano intendere che Pandolfo assisté alla contrastata elezione di Onorio II (15-16 dicembre 1124)."
