Phasathuen, W., N. Chinuntdej, N. Paopun, and K. Punthai. “Factors Influencing the Competitive Advantage of Thai Airfreight Forwarders”. Ph.D. In Social Sciences Journal, vol. 9, no. 3, Dec. 2019, pp. 830-44, https://so05.tci-thaijo.org/index.php/phdssj/article/view/153773.