O-Four was first mentioned in Republic Commando: Hard Contact a 2004 novel written by Karen Traviss. He later received mention in Republic Commando: Triple Zero, another book in the same series.
- The Complete Star Wars Encyclopedia
O-Four was first mentioned in Republic Commando: Hard Contact a 2004 novel written by Karen Traviss. He later received mention in Republic Commando: Triple Zero, another book in the same series.