Παραπομπή APA

Stephen R Covey. (1989). Seven habits of highly effective people. D C Books.

Παραπομπή Chicago Style

Stephen R Covey. Seven Habits of Highly Effective People. Kottayam: D C Books, 1989.

Παραπομπή MLA

Stephen R Covey. Seven Habits of Highly Effective People. D C Books, 1989.