Pecoraro, Alfonso, Anton Doubell, and Philip Herbst. “Double Atrial Heart Sound in a Patient With 2:1 Atrioventricular Block”. SA Heart Journal 14, no. 1 (April 5, 2017): 44–45. Accessed October 8, 2025. https://www.journals.ac.za/SAHJ/article/view/1879.