1. Allen, C. (2014). Umwelt or Umwelten? How should shared representations be understood given such diversity? Semiotica, 198, 137–158.
2. Armstrong, K. (2024). Chemical communication is nothing to sniff at. APS Observer, 37(1), (Dec. 11, 2023). https://www.psychologicalscience.org/observer/chemical-communication
3. Bacon, E. S., & Burghardt, G. M. (1976). Learning and color discrimination in the American black bear. International Conference on Bear Research and Management, 3, 27–36. (now Ursus).
4. Bierens de Haan, J. A. (1940). Die Tierschen Instinkte und ihr Umbau Durch Erfahrung. E. J. Brill.
5. Bierens de Haan, J. A. (1947). Animal psychology. Hutchinson.