"John Paul Twitchell", Religious Leaders of America, 2nd ed., Gale Group, 1999. Reproduced in Biography Resource Center, Farmington Hills, Michigan: Gale, 2009. http://galenet.galegroup.com/servlet/BioRC.
Bacon, Nicole (2001-08-30). Hadden, Jeffrey K. (ed.). Eckankar: The Religion of Light and Sound. University of Virginia Library, The Religious Movements Page. Archived from the original on 31 August 2006. Retrieved 10 July 2010.{{cite book}}: CS1 maint: bot: original URL status unknown (link)