Recommended Readings
Huxley, Aldous. The Perennial Philosophy. London: Chatto & Windus, 1946.
Maslow, Abraham H. Religions, Values, and Peak Experiences. Columbus, OH: Ohio State University Press, 1964.
Underhill, Evelyn. Mysticism: The Preeminent Study in the Nature and Development of Spiritual Consciousness. 1911.
Links
The Spiritual Guide
by Sri Swami Sivananda *
[* denotes an offsite source]