X Window System - Wikipedia

X Window System - Simple English Wikipedia, the free encyclopedia

1. Introduction to the X Window System - X Power Tools [Book]

Operating system - Wikipedia

X Window System - Wikipedia

What UNIX-based operating systems have support for GUI that is at least as strong as macOS's? - Quora

File:Xlib and XCB in the X Window System graphics stack.svg - Wikipedia

Windowing System: Graphical User Interface, Desktop Environment, Window Manager, Programmer, Typeface, Window Managers, X Window System : Surhone, Lambert M., Timpledon, Miriam T., Marseken, Susan F.: : Libri

X Window System – Wikipedia

Is Unix a GUI system? - Quora

Unix-like - Wikipedia