References for Joceline 5th/11th Earl Percy * of Northumberland
M.A.H., Marquis de Ruvigny: The Plantagenet roll of the blood royal, Essex Volume. London, Edinburgh, 1908
F.M.Powicke, E.B.Fryde: Handbook of British Chronology. London, 1961
D.Schwennicke: Europäische Stammtafeln, Vol. III/4, Tafel 713. Marburg, 1989