I keep posting them here.
How I got to learn about them?
Having a solid Informatics Engineering degree, with focus on systems programming, graphics and compilers, and a very nice university library.
That was it, we had to hunt for books, compuserve, gopher and BBS were still a thing.
Nowadays learning about the history of PL is a google/bing/... search away, a couple of seconds with access to plenty of scanned papers and conference proceddings since the early 60's, so one has to be quite lazy not to research them.