Hiby, Lex, Torkel Lundberg, Olle Karlsson, John Watkins, Mart Jüssi, Ivar Jüssi, and Björn Helander. 2007. “Estimates of the Size of the Baltic Grey Seal Population Based on Photo-Identification Data”. NAMMCO Scientific Publications 6 (January), 163-75. https://doi.org/10.7557/3.2731.