Loomis 2006, p. 4, note 3. "Our author gives two incompatible traditions, the first that Peter did not come to Rome before the reign of Nero, the second that after a pontificate of twenty-five years at Rome he was put to death under Nero. The latter is Jerome version". Loomis, Louise Ropes (2006) [1917]. The Book of the Popes (Liber Pontificalis). Arx Publishing, LLC. ISBN978-1-889758-86-2. (Ends with Pope Pelagius II, AD 579–90; English translation with scholarly footnotes and illustrations).
Eusebius, Ecclesiastical History, VIII, 13. "After Vespasian had reigned ten years Titus, his son, succeeded him. In the second year of his reign, Linus, who had been bishop of the church of Rome for twelve years, delivered his office to Anencletus."
Jerome, Chronicon, AD 80, 2nd year of Titus (Oct. 79–Oct. 80): "Cletus (also called Anencletus) is appointed second bishop of the Roman church for 12 years."