Barwal, Vijay Kumar, and Gopal Ashish Sharma. “IAPSM’s Textbook of Community Medicine”. International Journal Of Community Medicine And Public Health 6, no. 9 (August 27, 2019): 4131–4131. Accessed November 17, 2025. https://www.ijcmph.com/index.php/ijcmph/article/view/5239.