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Estes et al., 2009, p.1.650. Estes, J. A.;Doak, D. F.;Springer, A. M.;Williams, T. M.«Causes and consequences of marine mammal population declines in southwest Alaska: a food-web perspective»(en anglès).Philosophical Transactions of the Royal Society B: Biological Sciences,364,1524,2009,p.1.647–1.658. DOI: 10.1098/rstb.2008.0231. PMC: 2685424. PMID: 19451116.