* Snow, D. W.; Perrins, Christopher M.; Doherty, P. & Cramp, S. (1998): "The complete birds of the western Palaearctic on CD-ROM".
* Snow, D. W.; Perrins, Christopher M.; Doherty, P. & Cramp, S. (1998): "The complete birds of the western Palaearctic on CD-ROM".