STD's Today National Prevention Network, Center for Disease Control, United States Government, retrieving 2007
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Werdelin L, Nilsonne A (janeiro de 1999). «The evolution of the scrotum and testicular descent in mammals: a phylogenetic view». J. Theor. Biol. 196 (1): 61–72. PMID9892556. doi:10.1006/jtbi.1998.0821
Werdelin L, Nilsonne A (janeiro de 1999). «The evolution of the scrotum and testicular descent in mammals: a phylogenetic view». J. Theor. Biol. 196 (1): 61–72. PMID9892556. doi:10.1006/jtbi.1998.0821