Grant, P.J., K. Mullarney, L. Svensson, D. Zetterstrom, K. Mullarney (1999) Collins Bird Guide: The Most Complete Field Guide to the Birds of Britain and Europe. Harpercollins Pub Ltd ISBN 0 00 219728 6
Grant, P.J., K. Mullarney, L. Svensson, D. Zetterstrom, K. Mullarney (1999) Collins Bird Guide: The Most Complete Field Guide to the Birds of Britain and Europe. Harpercollins Pub Ltd ISBN 0 00 219728 6