(in Japanese)Zalophus californianus japonicus (CR), Red Data Book, Japan Integrated Biodiversity Information System, Ministry of the Environment (Japan). "The Japanese sea lion (Zalophus californianus japonicus) was common in the past around the coast of the Japanese Archipelago, but declined rapidly after the 1930s from overhunting and increased competition with commercial fisheries. The last record in Japan was a juvenile, captured in 1974 off the coast of Rebun Island, northern Hokkaido."
Lento, G.M.; Hickson, R.E.; Chambers, G.K.; Penny, D. (1 January 1995). "Use of spectral analysis to test hypotheses on the origin of pinnipeds". Molecular Biology and Evolution. 12 (1): 28–52. doi:10.1093/oxfordjournals.molbev.a040189. PMID7877495.
Wynen, L; Goldsworthy, SD; Insley, SJ; Adams, M; Bickham, JW; Francis, J; Gallo, JP; Hoelzel, AR; etal. (2001). "Phylogenetic relationships within the eared seals (Otariidae: Carnivora): implications for the historical biogeography of the family". Mol. Phylogenet. Evol. 21 (2): 270–284. Bibcode:2001MolPE..21..270W. doi:10.1006/mpev.2001.1012. PMID11697921.
Yonezawa, T.; etal. (2009). "The monophyletic origin of sea lions and fur seals (Carnivora; Otariidae) in the Southern Hemisphere". Gene. 441 (1–2): 89–99. doi:10.1016/j.gene.2009.01.022. PMID19254754.
Berta, A.; Churchill, M. (2012). "Pinniped Taxonomy: evidence for species and subspecies". Mammal Review. 42 (3): 207–234. doi:10.1111/j.1365-2907.2011.00193.x.
Lento, G.M.; Hickson, R.E.; Chambers, G.K.; Penny, D. (1 January 1995). "Use of spectral analysis to test hypotheses on the origin of pinnipeds". Molecular Biology and Evolution. 12 (1): 28–52. doi:10.1093/oxfordjournals.molbev.a040189. PMID7877495.
Wynen, L; Goldsworthy, SD; Insley, SJ; Adams, M; Bickham, JW; Francis, J; Gallo, JP; Hoelzel, AR; etal. (2001). "Phylogenetic relationships within the eared seals (Otariidae: Carnivora): implications for the historical biogeography of the family". Mol. Phylogenet. Evol. 21 (2): 270–284. Bibcode:2001MolPE..21..270W. doi:10.1006/mpev.2001.1012. PMID11697921.
Yonezawa, T.; etal. (2009). "The monophyletic origin of sea lions and fur seals (Carnivora; Otariidae) in the Southern Hemisphere". Gene. 441 (1–2): 89–99. doi:10.1016/j.gene.2009.01.022. PMID19254754.