C-9PO first appeared in the 1996 novel The New Rebellion, written by Kristine Kathryn Rusch. Another droid designated C-9PO appeared in the 1999 novel The New Jedi Order: Vector Prime, written by R. A. Salvatore. The two droids were confirmed to be separate characters by the entry for C-9PO in the 2008 reference book The Complete Star Wars Encyclopedia.
- Star Wars Encyclopedia
- The Essential Guide to Planets and Moons
- A Guide to the Star Wars Universe, Third Edition, Revised and Expanded
- The Complete Star Wars Encyclopedia