| title | ISBN-13 | year of publication |
|---|---|---|
| Aphorisms on Spiritual Method: Yoga Sutras of Patanjali in the Light of Mystical Experience | 978-0-86140-354-7 | 1993 |
| Old and New Evidence on the Meaning of Life: An Introduction to Scientific Mysticism v. 1: The Mystical World-view and Inner Contest | 978-0-86140-241-0 | 1986 |
| Old and New Evidence on the Meaning of Life: The Dynamics of Spiritual Development Dynamics of Spiritual Development v. 2: The Mystical World-view and Inner Contest | 978-0-86140-277-9 | 2000 |
| Universal Theology and Life in the Other Worlds | 978-0-86140-463-6 | 2007 |