Leelasiri, K., W. Pinyovivat, T. Jivapaisarnpong, and T. Kchacheewa. “The Study on the Cold Chain System of Vaccines Used in the EPI (OPV and DTP Vaccines)”. Journal of Health Science of Thailand, vol. 2, no. 1, Mar. 1993, pp. 41-48, https://thaidj.org/index.php/JHS/article/view/6148.