Who's Who in the Spirit World is a spirit guide that was used to conduct research on the Ghostmaster.
The Real GhostbustersEdit
"Who's Who in the Spirit World" has an entry on the Ghostmaster and states the Ghostmaster is a Class 11.  Ray Stantz checked a copy out from the New York City Public Library when he and the other Ghostbusters were battling the Ghostmaster. He revealed the troubling information to Egon Spengler after showing him the book.
- ↑ Ray Stantz (2009).The Real Ghostbusters- "Revenge of the Ghostmaster" (1989) (DVD ts. 09:36-09:39). Time Life Entertainment.