Covey, S. R. The 7 habits of highly effective people: Restoring the character ethic (Revised edition.).
Citazione stile Chigago Style (17a edizione)Covey, Stephen R. The 7 Habits of Highly Effective People: Restoring the Character Ethic. Revised edition.
Citatione MLA (8a ed.)Covey, Stephen R. The 7 Habits of Highly Effective People: Restoring the Character Ethic. Revised edition.
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