Froehlich, D.J. (2002). «Quo vadis eohippus? The systematics and taxonomy of the early Eocene equids (Perissodactyla)». Zoological Journal of the Linnean Society134 (2): 141-256. doi:10.1046/j.1096-3642.2002.00005.x.
Hooker, J.J. (1994). «The beginning of the equoid radiation». Zoological Journal of the Linnean Society112 (1–2): 29-63. doi:10.1006/zjls.1994.1033.