References for Henry 2nd/8th Earl Percy * of Northumberland
Sir B.Burke: The Dormant and Extinct Peerage. London, 1866
F.M.Powicke, E.B.Fryde: Handbook of British Chronology. London, 1961
D.Schwennicke: Europäische Stammtafeln, Vol. III/4, Tafel 713. Marburg, 1989