Perhaps outline the relationships between guardians and monitors in chapter 4

[knz]

I've attended the strangeloop talk and read the text in this repo, and I find it sad that O'Hare's work on CSP and Milner's pi-calculus are barely mentioned.

Maybe you can choose to keep them out of scope, but I think it would still be important to remind the reader in chapter 4 that Argus' "guardians" are just a custom name for the concept of monitor, invented by O'Hare in 1974, widely used by that time already, and subsequently used with that name in Java and most other concurrent and distributed languages/frameworks afterwards.