Phoosuwan, T., and U. . Muangsan. “Cauasal Factors Affecting Team Leader Competency and Operating Results of Direct Sales Business in Thailand”. Rajapark Journal, vol. 16, no. 48, Oct. 2022, pp. 331-48, https://so05.tci-thaijo.org/index.php/RJPJ/article/view/258381.