X.Org Manual pages: Section 7
- X - a portable, network-transparent
window system
- X.Org - X.Org Group information
- XConsortium - X Consortium information
- XProjectTeam - X.Org Group information
- XStandards - X Window System Standards
and Specifications
- Xprint - The "X print service" - a portable, network-transparent printing
system based on the X11 protocol
- Xsecurity - X display access control