Religious Requirements and Practices of Certain Selected Groups: A Handbook for Chaplains, By U. S. Department of the Army, Published by The Minerva Group, Inc., 2001, ISBN0-89875-607-3, ISBN978-0-89875-607-4, page 1–42. Google books listing
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Ferdinando, Keith (1995). "SIckness and Syncretism in the African Context". In Billington, Antony (ed.). Mission and Meaning(PDF). Paternoster Press. p. 265. ISBN0-85364-676-7. Retrieved 31 October 2016.