Inthana, K., S. Koednok, and W. Rojchanapaphaporn. “Causal Factors Influencing Customer Loyalty of Private Parcel Delivery Businesses in Thailand”. Rajapark Journal, vol. 18, no. 57, Apr. 2024, pp. 379-97, https://so05.tci-thaijo.org/index.php/RJPJ/article/view/270478.