Otto, Rudolph
Mysticism east and west: a comparative analysis of the nature of mysticism
Meridian Books, 1957
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Collins, John Edward
Mysticism and new paradigm psychology
Rowman & Littlefield, 1991
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Nicholson, Reynold Alleyne
Studies in Islamic mysticism
University Press , 1967
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Al-Attas, Syed Muhammad Naguib
Mysticism of Hamzah Fansuri
Kuala Lumpur : University of Malay Press, 1970.
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Khan, Hazrat Inayat
Philosophy, Psychology, Mysticism
The Sufi International Headquarter's, 1956
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