^In published writings, the term appears in 1952 for Tillich and in 1953 for Zimmer. Since the two men were personally acquainted, it is difficult to say which of them coined the term. Note that the term transtheism is avoided by both.
^Antonio Rigopoulos, The Life and Teachings of Sai Baba of Shirdi (1993), p. 372; J. L. (Ed) Houlden, Jesus: The Complete Guide (2005), p. 390
^Steven T. Katz, Mysticism and Sacred Scripture, Oxford University Press (2000), p. 177 ; Pulasth Soobah. Roodurmun, Kanshi Ram, Bhāmatī and Vivaraṇa Schools of Advaita Vedānta, Motilal Banarsidass (2002), p. 172
^Werner Karel, Love Divine: Studies in Bhakti and Devotional Mysticism (1993), p. 153