Comment by pjmlp

What opened my eyes beyond UNIX was having a great library at the university where I could dive into alternative realities.

Luckily many of the same books and papers, now live on as facsimle copies on bitsavers, archive and many other Internet and Faculty repositories.

Burroughs, Xerox PARC, ETHZ, TI, Genera, VMS, Lisa, Constellation, SOLO, SPIN and plenty others are available for systems programming archeology.