Silaket, S. . “Investigation of Beak-Even Point for Variable Refrigerant Flow Air Conditioning System in Office Building”. Journal of Energy and Environment Technology of Graduate School Siam Technology College, vol. 8, no. 2, Dec. 2021, pp. 79-90, https://ph01.tci-thaijo.org/index.php/JEET/article/view/245951.