Härkönen, T., S. Brasseur, J. Teilmann, C. Vincent, R. Dietz, K. Abt, and P. Reijnders. “Status of Grey Seals Along Mainland Europe from the Southwestern Baltic to France”. NAMMCO Scientific Publications, vol. 6, Jan. 2007, pp. 57-68, doi:10.7557/3.2721.