Freeman, Gary (30 June 2010). "Comment on Xiao et al. (2009), response to: the rise of bilaterians". Historical Biology. 22 (4): 430–432. doi:10.1080/08912960903562259. S2CID85339496.
Freeman, Gary (30 June 2010). "Comment on Xiao et al. (2009), response to: the rise of bilaterians". Historical Biology. 22 (4): 430–432. doi:10.1080/08912960903562259. S2CID85339496.