Schild, Romuald, and Fred Wendorf. “Ambiguity of Ecological Conditioning of Great Cultural | Transformations. Two Examples: European Plains at the End of the Ice Age and Early Holocene Sahara”. Anthropological Review, vol. 44, no. 1, June 1978, pp. 157-73, doi:10.18778/1898-6773.44.1.15.