Why Won't You Apologize?: Healing Big Betrayals and Everyday Hurts by Harriet Lerner PhD, Cassandra Campbell, et al.
Sorry About That: The Language of Public Apology. By Edwin Battistella
When Sorry Isn't Enough: Making Things Right with Those You Love by Gary Chapman and Jennifer Thomas
Art of the Apology: How, When, and Why to Give and Accept Apologies by Lauren M. Bloom
Effective Apology: Mending Fences, Building Bridges, and Restoring Trust by John Kador
On Apology by Aaron Lazare
The Power of Apology: Healing Steps to Transform All Your Relationships by Beverly Engel
The Five Languages of Apology by Gary Chapman