(en) Kyle Orland, Dave Thomas et Scott Steinberg, The Videogame Style Guide and Reference Manual, Lulu.com, (ISBN978-1-4303-1305-2, lire en ligne), p. 40
(en) Shanna Compton, Gamers: Writers, Artists & Programmers on the Pleasures of Pixels, Soft Skull Press, (ISBN978-1-932360-57-8, lire en ligne), p. 117-118
flylib.com
(en) Richard Rouse III, Game Design: Theory and Practice, Second Edition: Theory and Practice, Second Edition, Jones & Bartlett Learning, (ISBN978-1-4496-3345-5, lire en ligne), p. 60