Abubakar, Hafiz, Ali Antoni, Johnwan Usman, Iskandar Lubis, and RA. Erma. 2017. “Missed Opportunities for Immunization at The Out-Patient Clinic: Prevalence and Related Factors”. Paediatrica Indonesiana 36 (7-8), 146-54. https://doi.org/10.14238/pi36.7-8.1996.146-54.