Endo, H.; Sakata, S.; Arai, T.; Miyazaki, N. (април 2001). „The Muscles of Mastication in the Caspian Seal (Phoca caspica)”. Anatomia, Histologia, Embryologia. 31 (5): 262—265. PMID12484416. doi:10.1046/j.1439-0264.2002.00372.x.
Harkonen, Tero; Jüssi, Mart; Baimukanov, Mirgaly; Bignert, Anders; Dmitrieva, Lilia; Kasimbekov, Yesbol; Verevkin, Mikhail; Wilson, Susan; Goodman, Simon J. (јул 2008). „Pup Production and Breeding Distribution of the Caspian Seal (Phoca caspica) in Relation to Human Impacts”. AMBIO: A Journal of the Human Environment. 37 (5): 356—361. PMID18828281. doi:10.1579/07-r-345.1.
Endo, H.; Sakata, S.; Arai, T.; Miyazaki, N. (април 2001). „The Muscles of Mastication in the Caspian Seal (Phoca caspica)”. Anatomia, Histologia, Embryologia. 31 (5): 262—265. PMID12484416. doi:10.1046/j.1439-0264.2002.00372.x.
Harkonen, Tero; Jüssi, Mart; Baimukanov, Mirgaly; Bignert, Anders; Dmitrieva, Lilia; Kasimbekov, Yesbol; Verevkin, Mikhail; Wilson, Susan; Goodman, Simon J. (јул 2008). „Pup Production and Breeding Distribution of the Caspian Seal (Phoca caspica) in Relation to Human Impacts”. AMBIO: A Journal of the Human Environment. 37 (5): 356—361. PMID18828281. doi:10.1579/07-r-345.1.