APA (7th ed.) Citation

Card, O. S. (1991). Ender's game (Rev. ed.). Tor.

Chicago Style (17th ed.) Citation

Card, Orson Scott. Ender's Game. Rev. ed. New York: Tor, 1991.

MLA (8th ed.) Citation

Card, Orson Scott. Ender's Game. Rev. ed. Tor, 1991.