Almaas, A.H.
    Diamond Heart, Books 1 - 4
    Berkeley, CA: Diamond Books, 1987-1997
    Facets of Unity
    Berkeley, CA: Diamond Books, 1998

  Gore, Belinda
    Ecstatic Body Postures: An Alternate Reality Workbook
    Santa Fe, NM: Bear & Company, 1995

  Maitri, Sandra
    The Spiritual Dimension of the Enneagram:
    Nine Faces of the Soul
    New York: Tarcher/Putnam, 2000

  Riso, Don Richard
    Enneagram Transformations: Releases and Affirmations
    for Healing Your Personality Type
    Boston: Houghton Mifflin, 1993

  Riso, Don Richard & Hudson, Russ
    Personality Types: Using the Enneagram for
    Self-Discovery (Revised Edition)
    Boston: Houghton Mifflin, 1996

    The Wisdom of the Enneagram: The Complete Guide
    to Psychological and Spiritual Growth for the Nine
    Personality Types
    New York: Bantam Books, 1999

    Understanding the Enneagram: The Practical Guide
    to Personality Types (Revised Edition)
    Boston: Houghton Mifflin, 2000