COVEY, S. R. (1990). The 7 habits of higly effective people: Powerful lessonin personal change. A Fireside Book.
Lua i Stíl Chicago (17ú heag.)COVEY, Stephen R. The 7 Habits of Higly Effective People: Powerful Lessonin Personal Change. New York: A Fireside Book, 1990.
Lua MLA (9ú heag.)COVEY, Stephen R. The 7 Habits of Higly Effective People: Powerful Lessonin Personal Change. A Fireside Book, 1990.
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