ISBN 0-7470-1410-8* Malling Olsen, Klaus and Hans Larsson, "Gulls of Europe, Asia and North America" ISBN 0-7136-7087-8
ISBN 0-7470-1410-8* Malling Olsen, Klaus and Hans Larsson, "Gulls of Europe, Asia and North America" ISBN 0-7136-7087-8* BirdLife Species Factsheet