Covey, S. R. (1991). Principle-Centred Leadership. Pocket Books.
Chicagoスタイル(17版)引用形式Covey, Stephen R. Principle-Centred Leadership. London: Pocket Books, 1991.
MLA(9版)引用形式Covey, Stephen R. Principle-Centred Leadership. Pocket Books, 1991.
警告: この引用は必ずしも正確ではありません.