1. The Grey seal and Common seal in European waters;Bonner W. N.;Oceanogr. Mar. Biol. Ann. Rev.,1972
2. Grey seal marking at North Rona;Campbell N.;Salmon Net.,1966
3. Growth and Movements of a Known-Age Harbor Seal
4. The cause of fluctuations in the seal population (Pfioca vitulina) in the Dutch coastal waters;Haaften J. L.;ICES CM,1972