Martinelli, Dario. “The Musical Circle: The Umwelt Theory, As Applied to Zoomusicology”. Sign Systems Studies 32, no. 1/2 (December 31, 2004): 229–252. Accessed December 26, 2024. https://ojs.utlib.ee/index.php/sss/article/view/SSS.2004.32.1-2.10.