APA
Stephen R. Covey, . (1991). Principle-centered leadership. New York: Simon & Schuster.
Chicago
Stephen R. Covey, . 1991. Principle-centered leadership. New York: Simon & Schuster.
Harvard
Stephen R. Covey, . (1991). Principle-centered leadership. New York: Simon & Schuster.
MLA
Stephen R. Covey, . Principle-centered leadership. New York: Simon & Schuster. 1991.
