Bill Pronzini and Marcia Muller's novel Double is a team-up between Pronzini's Nameless Detective and Muller's P.I. Sharon McCone, who meet at a convention in San Diego. Also attending the convention are Sue Grafton's Kinsey Millhone, Robert J. Randisi's Miles Jacoby, and William Campbell Gault's Brock "The Rock" Callahan. In Gault's The Cana Diversion, Callahan investigates the death of his friend and fellow P.I. Joe Puma, who appeared in his own series of novels by Gault from 1953 to 1961.