"Equidae." . . . . "Horses." . . "Zebras." . . "Equidae (Perissodactyla)" . . . . . . . "The horse and its relatives/ by R. Lydekker" . . . . "The Horse and its relatives" . . . "The horse and its relatives"@en . "The horse and its relatives" . . . . . . . "The Horse and its relatives. [With illustrations.]"@en . . . . . . . . . . . . . . . . . . . . . . "Mule." . .