Link: The MGR Window System
The MGR Window System (via) is a brief introduction to MGR, an interesting and under-mentioned Unix windowing system, including a screenshot. I once used MGR myself and have reasonably fond memories of it, so it's nice to see more writing about it on the Internet.
(And looking at my old entry I see that I linked to this article there in HTTP version. Still, I encourage you to read about MGR. It's a path not taken in Unix window systems.)