Rachel A. Kuhn, Hermann Ansorge, Szymon Godynicki og Wilfried Meyer (2010). «Hair density in the Eurasian otter Lutra lutra and the Sea otter Enhydra lutris». Acta Theriologica. 55 (3): 211–222. doi:10.4098/j.at.0001-7051.014.2009. «Lutra lutra exhibited a mean hair density of about 70 000 hairs/cm2 (whole body, appendages excepted), the mean individual density ranging from about 60 000 to 80 000 hairs/cm2. The dominant hair type were secondary hairs (wool hairs), the hair coat comprising only 1.26% of primary hairs (PH).»
Park, H. C., Kurihara, N., Kim, K. S., Min, M. S., Han, S., Lee, H., & Kimura, J. (2019). What is the taxonomic status of East Asian otter species based on molecular evidence?: focus on the position of the Japanese otter holotype specimen from museum. Animal cells and systems, 23(3), 228-234. DOI: 10.1080/19768354.2019.1601133
