1001 Ways to Reward Employees by Bob Nelson

FYI (For Your Improvement) by Michael Lombardo & Robert Eichinger

Quiet: The Power of Introverts in a World That Can't Stop Talking by Susan Cain

You Don’t Need a Title to Be A Leader by Mark Sanborn

The Speed of Trust by Stephen M.R. Covey

How to Win Friends and Influence People by Dale Carnegie