1. The Signs of All Times: Entoptic Phenomena in Upper Palaeolithic Art [and Comments and Reply]
2. M. Aldhouse-Green , S. Aldhouse-Green , The Quest for the Shaman: Shape-Shifters (Sorcerers and Spirits, Thames, New York, NY, 2005).
3. D. S. Whitley , Cave Paintings and the Human Spirit: The Origin and Creativity and Belief (Prometheus Books, Amherst, NY, 2009).
4. P. Vitebsky , Shamanism (University of Oklahoma Press, Norman, OK, 1995).
5. G. Gutiérrez , M. E. Pye , “Iconography of the Nahual: Human-animal transformation in Preclassic Guerrero and Morelos: Archaeology and ethnography of shape-shifters in Mesoamerica” in The Place of Stone Monuments: Context, Use, and Meaning in Mesoamerica’s Transition, J. Guernsey, J. E. Clark, B. Arroyo, Eds. (Dumbarton Oaks, Washington, DC, 2010), pp. 27–54.