Tønnessen, Morten. “The Ontogeny of the Embryonic, Foetal and Infant Human Umwelt”. Sign Systems Studies 42, no. 2/3 (December 5, 2014): 281–307. Accessed April 26, 2024. https://ojs.utlib.ee/index.php/sss/article/view/SSS.2014.42.2-3.06.