Burke's Genealogical History of the Dormant, Abeyant, Forfeited @ Calls him Robert de Ferrers
The cited information was published by Burke's Peerage, London, 1866 (Ref: Calls him Robert de Ferrers) The author/originator was Burke's Peerage.
Source Notes
TITL Burke's Genealogical History of the Dormant, Abeyant, Forfeited
& Extinct Peerages of the British EmpireABBR Burke's Dormant Peerage