Kent Kraft. The Eye Sees More Than the Heart Knows: The Visionary Cosmology of Hildegard of Bingen. University Microfilms: PhD. diss. Univ. of Wisconsin-Madison, 1978. Pages 97, 106. Cited in King-Lenzmeier, 48 and 204; See also: Keizer, Gerrit J. (2013). "Hildegard of Bingen: Unveiling the Secrets of a Medieval High Priestess and Visionary". (Chapter 4). In John Rush (Ed.). Entheogens and the Development of Culture. Berkeley: North Atlantic Books. pp. 85-210. ISBN9781583946244. OCLC873807930.
