Punnanan, Chonnapha. “NINE KEYS PHILOSOPHY FOR HUMAN RESOURCE DEVELOPMENT BY PALANGJIT DHAMMA JAKRAWAN INSTITUTE”. Journal of MCU Nakhondhat 7, no. 5 (May 20, 2020): 12–20. Accessed May 7, 2024. https://so03.tci-thaijo.org/index.php/JMND/article/view/243116.