• [Wiki] https://en.wikipedia.org/wiki/Grey_seal.
• [AnAge] http://genomics.senescence.info/species/entry.php?species=Halichoerus_grypus.
• [Hauk2007] Hauksson, E. (2007). Growth and reproduction in the Icelandic grey seal. NAMMCO Scientific Publications, pages 153--162. doi:10.7557/3.2730.
• [Kooy2010] Kooijman, S. (2010). Dynamic Energy Budget theory for metabolic organisation. Cambridge Univ. Press, Cambridge.