Covey, S. R. (1991). Principle-centered leadershipages (First edition.). A Fireside Book.
Chicago-čujuhus (17. p.)Covey, Stephen R. Principle-centered Leadershipages. First edition. New York: A Fireside Book, 1991.
MLA-čujuhus (9. p.)Covey, Stephen R. Principle-centered Leadershipages. First edition. A Fireside Book, 1991.
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