PSP = "Personal Software Process", the step before TSP, "Team Software Process".
Personal software process (PSP): https://en.wikipedia.org/wiki/Personal_software_process
Team software process (TSP): https://en.wikipedia.org/wiki/Team_software_process
It's there for anyone who is interested. Right now I'm skimming it to see what I can learn. Can be quite involved but can reduce errors and improve quality by orders of magnitude. (Proven.)
Given that, Humphrey repeatedly emphasizes that communication and understanding about what needs to be built are the most important parts, and that trying to test quality into larger systems can literally take years (of full-time work, by teams of dozens of developers).
Since I'm retired and reviewing all the ways that I wasted my life, then for me it's only an intellectual exercise, but this could help someone still in the thick of it. Lots of food for thought.