(EN) Heath W. Lowry, The nature of the early Ottoman state, State University of New York Press, 2003, p. 153, ISBN 1-4175-2407-3, OCLC 55896257. URL consultato il 13 dicembre 2022.
«Mother of Bayezid II was Gülbahar Hatun (a Pontic Greek from the village of Douvera in Trabzon)»