Lerssongkram, N., S. Pinitsoontorn, and N. Keawprak. “Synthesis and thermoelectric properties of Ca3Co4O9 prepared by sol-gel method using ova”. Asia-Pacific Journal of Science and Technology, vol. 16, no. 1, Apr. 2017, pp. 11-19, https://so01.tci-thaijo.org/index.php/APST/article/view/83163.