APA (7th ed.) Citation

Quercia, V., & O'Reilly, T. (1993). X Window system: User's guide for X11 release 5. O'Reilly.

Chicago Style (17th ed.) Citation

Quercia, Valerie, and Tim O'Reilly. X Window System: User's Guide for X11 Release 5. Sebastopol: O'Reilly, 1993.

MLA (9th ed.) Citation

Quercia, Valerie, and Tim O'Reilly. X Window System: User's Guide for X11 Release 5. O'Reilly, 1993.