Gutmann, Mathias. “Uexküll and Contemporary Biology: Some Methodological Reconsiderations”. Sign Systems Studies 32, no. 1/2 (December 31, 2004): 169–186. Accessed March 28, 2024. https://ojs.utlib.ee/index.php/sss/article/view/SSS.2004.32.1-2.07.