Lewis Spence. (2011). Encyclopedia of Occultism and Parapsychology. Kessinger Publishing.
Joe Nickell. (2001). Real-Life X-Files: Investigating the Paranormal. The University Press of Kentucky. pp. 260–261. Also see Joe Nickell. (2005). Camera Clues: A Handbook for Photographic Investigation. The University Press of Kentucky. p. 151
Ronald Pearsall. (1972). The Table-Rappers. Book Club Associates. pp. 118–125