computer - history - pdp-10 - pdp-11 - plan9 - Unix -
Guides how to install or run older UNIX versions in simh.
Also the UNIX Programmer's manual of V1-V6. V1-V6 are available as nroff output converted to html. V4-V6 are also available as troff'ed PDFs.
The site also has information about Plan 9 and pdp-6/pdp-10.