APA
Covey S. R., . (1989). The seven habits of highly effective people. New York: Simon and Schuster.
Chicago
Covey Stephen R, . 1989. The seven habits of highly effective people. New York: Simon and Schuster.
Harvard
Covey S. R., . (1989). The seven habits of highly effective people. New York: Simon and Schuster.
MLA
Covey Stephen R, . The seven habits of highly effective people. New York: Simon and Schuster. 1989.