Covey, S. R. (1992). Principle-centered leadership. Simon & Schuster.
Chicagoスタイル(17版)引用形式Covey, Stephen R. Principle-centered Leadership. New York, N.Y.: Simon & Schuster, 1992.
MLA(8版)引用形式Covey, Stephen R. Principle-centered Leadership. Simon & Schuster, 1992.
警告: この引用は必ずしも正確ではありません.