Pham, Ha, and Tri Tran. “Coding System: A Source of Variability in Reported Prevalence Rates of Atrial Septal Defect”. Online Journal of Public Health Informatics 6, no. 1 (March 9, 2014). Accessed January 29, 2022. https://ojphi.org/ojs/index.php/ojphi/article/view/5058.