Covey, S. R. (1989). The seven habits of highly effective people: Restoring the character ethic. Simon and Schuster.
Chicago-viite (17. p.)Covey, Stephen R. The Seven Habits of Highly Effective People: Restoring the Character Ethic. New York: Simon and Schuster, 1989.
MLA-viite (8. p.)Covey, Stephen R. The Seven Habits of Highly Effective People: Restoring the Character Ethic. Simon and Schuster, 1989.
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