Daniels, D. N., & Price, V. A. (2009). The essential enneagram: The definitive personality test and self-discovery guide (Revised and updated.). HarperOne.
Chicago Style (17th ed.) CitationDaniels, David N., and Virginia Ann Price. The Essential Enneagram: The Definitive Personality Test and Self-discovery Guide. Revised and updated. New York: HarperOne, 2009.
MLA (9th ed.) CitationDaniels, David N., and Virginia Ann Price. The Essential Enneagram: The Definitive Personality Test and Self-discovery Guide. Revised and updated. HarperOne, 2009.
Warning: These citations may not always be 100% accurate.