Herewith some interesting (somewhat) contemporary papers on early windowing systems:
1. There was a conference in the UK early in 1985 discussing the state of window systems
on Unix. Much interesting discussion and two talks by James Gosling, one about NeWS (then
still called SunDew), and one about what seems to be SunWindows. It would seem then that
these were developed almost in parallel.
http://www.chilton-computing.org.uk/inf/literature/books/wm/contents.htm
2. Then there is a 1986 paper by James Gettys, discussing the 18 month journey towards
X10. In particular it focuses on the constraints that Unix set on the design of the X
system.
https://www.tech-insider.org/unix/research/acrobat/860201-b.pdf
3. Next is the 1989 NeWS book that has a nice overview and history of windowing systems in
its chapter 3:
http://bitsavers.trailing-edge.com/pdf/sun/NeWS/The_NeWS_Book_1989.pdf
Both the UK conference and the NeWS book mention a Unix kernel-based windowing system done
at MIT in 1981 or 1982, “NU" or “NUnix”, by Jack Test. That one had not been
mentioned before here and may have been the first graphical windowing work on Unix,
preceding the Blit. Who remembers this one?
4. Finally, an undated paper by Stephen Uhler discussing the design of MGR is here:
https://sau.homeip.net/papers/arch.pdf
I’ve not included Rob Pike’s papers, as I assume they are well known on this list.
Some of the above papers may be worthy of stable archiving.