Covey, S. R. (1989). The 7 habits of highly effective people: Restoring the character ethic. Pocket books.
Chicago-tyylinen lähdeviittausCovey, Stephen R. The 7 Habits of Highly Effective People: Restoring the Character Ethic. London: Pocket books, 1989.
MLA-viiteCovey, Stephen R. The 7 Habits of Highly Effective People: Restoring the Character Ethic. Pocket books, 1989.
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