The thesis itself is at http://erlang.org/download/armstrong_thesis_2003.pdf
Joe Thesis is probably the best place to begin with.
That is so sad, he was in his late 60s and it seemed like he had a lot of life left in him, talking about how software can get better and having a great (and sometimes snarky) outlook on the profession.
Highly recommend his thesis (2003) and a few of his great interviews/presentations for anyone who isn’t familiar with Joe, it captures a lot of what he thought about and pushed for in his professional life.
I hope his family and friends can find some comfort in how much he was appreciated and admired in the development community.