Turovski, Aleksei. “The Semiotics of Animal Freedom: A zoologist’s Attempt to Perceive the Semiotic Aim of H. Hediger”. Sign Systems Studies 28 (December 31, 2000): 380–387. Accessed April 25, 2024. https://ojs.utlib.ee/index.php/sss/article/view/SSS.2000.28.20.