Ellis, Treenuch, Artit Hutem, and Akgabutkhan Pathan. 2019. “Models for Calculation of Global Solar Radiation from Meteorological Data for Phetchabun Province”. Princess of Naradhiwas University Journal 11 (2):132-41. https://li01.tci-thaijo.org/index.php/pnujr/article/view/123146.