LieDr.med, Birgit; psychol, RVTS sør/SSHF og medlem av den europeiske torturkomitéNora SveaassDr; torturkomité, medlem av FNs (26. juni 2008). «Med rett til å torturere». Dagbladet.no (på norsk). Besøkt 30. juli 2019.
Zabel, G. «Art, Shamanism, and Entoptic Images». University of Massachusetts, Boston. Besøkt 6. august 2019. «Lewis-Williams has argued that the form-constants that Kluver identified also underlie the geometric images of Paleolithic European cave art. The bridge that connects the two is the common neurological makeup that the Bushman, and all currently living human beings, share with the Paleolithic hunters. When the human brain is destabilized in certain ways - through sensory deprivation, rhythmic chanting or drumming, flickering lights, certain forms of dance, as well as the ingestion of hallucinogenic drugs - it reacts by generating so-called "entoptic images," which are merely expressions of Kluver's form-constants»
