An alternative date of birth occasionally given is 1168 (van Dieten 1975,第169頁), based on William of Tyre's statement that Alexios was 13 in 1180. For discussion, concluding that 14 September 1169 is correct, see (Wirth 1956); (Magoulias 1984,第383頁). van Dieten, J. L., editor, Nicetae Choniatae historia, Berlin: De Gruyter, 1975 Wirth, Peter, Wann wurde Kaiser Alexios II. geboren? [When was Emperor Alexios II born?], Byzantinische Zeitschrift, 1956, 49: 65–67, doi:10.1515/byzs.1956.49.1.65 Magoulias, Harry J., translator, O city of Byzantium: annals of Niketas Choniates, Detroit: Wayne State University Press, 1984, ISBN 0-8143-1764-2