Jerome, Chronicon, AD 108, 11th year of Trajan. "Alexander holds the fifth episcopate of the city of Rome for ten years." This may be a mistake, as the accession of Sixtus is dated to the 3rd year of Hadrian, AD 119.
Liberian Catalogue; "11 years, 2 months, 1 day. He was in the time of Trajan, from the consulate of Palma and Tullus [109] to that of Velianus and Vetus [116]." The catalogue is full of errors and contradictions; the years given do not even match the length given in the same entry.