This PDF is an exerpt from the book Programming Distributed Computing Systems: A Foundational Approach by Professor Carlos Varela. He was my advisor at RPI, and one of the most pleasant professors I had the pleasure of interacting with during my time there. His classes were notoriously hard, but I enjoyed them very much. The full book includes very concise walk thoughs of various other less well known calculi and theoretical distributed programming models (in particular, the AMST lambda calculus actor model). If you like language or concurrency theory I highly recommend picking up a copy.