Chiangkul, A., and P. Sangkapreecha. “Digital Marketing Communication of Small and Medium Enterprises and the Decision Making in Hiring Advertising Agency”. Journal of Siam Communication Arts Review, vol. 21, no. 1, Apr. 2022, pp. 196-09, https://so05.tci-thaijo.org/index.php/commartsreviewsiamu/article/view/258771.