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Stephen R. Covey (1994). “Daily Reflections for Highly Effective People: Living THE SEVEN HABITS OF HIGHLY SUCCESSFUL PEOPLE Every Day”, p.111, Simon and Schuster
Stephen R. Covey (2015). “The Stephen R. Covey Interactive Reader - 4 Books in 1: The 7 Habits of Highly Effective People, First Things First, and the Best of the Most Renowned Leadership Teacher of our Time”, p.214, Mango Media Inc.