L. Trut, «Early Canid Domestication: The Farm-Fox Experiment,» American Scientist 87 (1999): 160, doi: 10.1511/1999.2.160; L. Trut, E. Naumenko, and D. Belyaev, «Change in Pituitary-Adrenal Function in Silver Foxes under Selection for Domestication,» Genetika 5 (1972): 35–43 (in Russian, English abstract).