1. Ultrasonographic characterization of reproductive anatomy and early embryonic detection in the Northern fur seal (Callorhinus ursinus) in the field;Adams;Mar. Mammal Sci.,2007
2. Reproductive biology of seals;Atkinson;Rev. Reprod.,1997
3. Bergfelt, D.R., Steinetz, B.G., Testa, J.W., Adams, G.P., 2008. Relaxin: a potential hormonal marker of pregnancy in Northern fur seals (Callorhinus ursinus). In: Association of Zoos and Aquariums 84th Annual Conference, Milwaukee, Wisconsin, USA (http://www.aza.org/AZAPublications/ConfPro/index.html).
4. Environmental and physiological factors controlling the reproductive cycles in pinnipeds;Boyd;Can. J. Zool.,1991
5. Reproduction in marine mammals;Boyd,1999