Peter Whitfield, The Image of the World, p.70. admin Peter Whitfield, The Charting of the Oceans: Ten Centuries of Maritime Maps (British Library, 1996), pp. 86-7 Pflederer, Finding Their Way at Sea: The Story of Portolan Charts, the Cartographers who Drew Them and the Mariners who Sailed by Them, (Houten: Hes & De Graaf, 2012), 98.