Linse P; Shermer M (2002). The Skeptic encyclopedia of pseudoscience. Santa Barbara, Calif: ABC-CLIO. pp. 206–7. ISBN1-57607-653-9.{{cite book}}: תחזוקה - ציטוט: multiple names: authors list (link)
Carroll RT (2003). The Skeptic's Dictionary: a collection of strange beliefs, amusing deceptions, and dangerous delusions. New York: Wiley. pp. 276–7. ISBN0-471-27242-6.