APA (7th ed.) Zitazioa

Covey, S. R. (1991). Principle-centered leadershipages (First edition.). A Fireside Book.

Chicago Style (17th ed.) Zitazioa

Covey, Stephen R. Principle-centered Leadershipages. First edition. New York: A Fireside Book, 1991.

MLA (9th ed.) Zitazioa

Covey, Stephen R. Principle-centered Leadershipages. First edition. A Fireside Book, 1991.