This first link is to Amy Edmondson's original research paper on the subject of psychological safety:

• Psychological Safety and Learning Behavior in Work Teams, Amy Edmondson, Administrative Science Quarterly, Vol 44, Issue 2, pp. 350 - 383, First Published June 1, 1999, https://doi.org/10.2307/2666999 

This is the New York Times report on Project Aristotle, the project that Google ran to find out what made some of its teams more successful than others:

• https://www.nytimes.com/2016/02/28/magazine/what-google-learned-from-its-quest-to-build-the-perfect-team.html

This article from Harvard Business Review gives important pointers on how to create a psychologically safe environment for our teams: 

• https://hbr.org/2017/08/high-performing-teams-need-psychological-safety-heres-how-to-create-it