Helpful information to start:
Nonviolent Communication (NVC): A Language of Life, Marshall Rosenberg
Self-compassion Skills Workbook, Tim Desmond | The Mindful Self-Compassion Workbook, Chris Germer (CMSC)
Complex PTSD: From Surviving to Thriving, Pete Walker (CPTSD)
The Body Keeps the Score, Bessel van der Kolt
Hold Me Tight, Sue Johnson
Attachment Theory research
Why do I feel depressed? series