Permin, Henrik, and Svend Norn. “Stethoscope - Over 200 Years”. Journal of Pulmonology and Respiratory Research 3, no. 1 (January 18, 2019): 001–008. Accessed October 10, 2025. https://www.pulmonolrespirjournal.com/jprr/article/view/jprr-aid1010.