Cita APA (7th ed.)
Covey, S. R. (1991). Principle-centered leadership. Pocket books.
Cita Chicago (17th ed.)
Covey, Stephen R. Principle-centered Leadership. London: Pocket books, 1991.
Cita MLA (9th ed.)
Covey, Stephen R. Principle-centered Leadership. Pocket books, 1991.
Atenció: Aquestes cites poden no estar 100% correctes.