Nonfiction writer Stephen R. Covey has died. He was 79 years old.

In 1989, Covey (pictured, via) published the bestselling self-help book, The Seven Habits of Highly Effective People. According to The Huffington Post, The Seven Habits of Highly Effective People have sold more than 20 million copies in 38 languages throughout the world.

He also wrote The 8th Habit: From Effectiveness to Greatness and The Leader in Me—How Schools and Parents Around the World Are Inspiring Greatness, One Child at a Time.

Here’s more from his official obituary: “In 1984, Dr. Covey made the decision to leave full-time teaching as a university professor to establish a business organization, Covey Leadership Center, that could take principle-centered leadership throughout the world. From the inception of that business, Dr. Covey’s focus was always on writing and teaching, leaving the leadership and management of the business to others.”