Blackburn DG, Flemming AF (2012). "Invasive implantation and intimate placental associations in a placentotrophic African lizard, Trachylepis ivensi (scincidae)". J. Morphol. 273 (2): 137–59. doi:10.1002/jmor.11011. PMID21956253. S2CID5191828.
Neill, Wilfred T. (January 1964). "Viviparity in Snakes: Some Ecological and Zoogeographical Considerations". The American Naturalist. 98 (898): 35–55. doi:10.1086/282299. S2CID85209921.
"Birth and care of young". Animals: Sharks and rays. Busch Entertainment Corporation. Archived from the original on August 3, 2013. Retrieved 2013-08-28.
Blackburn DG, Flemming AF (2012). "Invasive implantation and intimate placental associations in a placentotrophic African lizard, Trachylepis ivensi (scincidae)". J. Morphol. 273 (2): 137–59. doi:10.1002/jmor.11011. PMID21956253. S2CID5191828.
Neill, Wilfred T. (January 1964). "Viviparity in Snakes: Some Ecological and Zoogeographical Considerations". The American Naturalist. 98 (898): 35–55. doi:10.1086/282299. S2CID85209921.
"Birth and care of young". Animals: Sharks and rays. Busch Entertainment Corporation. Archived from the original on August 3, 2013. Retrieved 2013-08-28.