Likitsarun, N., and et al. “The Level of Tourist’s Opinion on the Use of Marketing Mixed Factors for the Tourism Management in Phichit Province, Thailand”. Journal of Thai Hospitality and Tourism, vol. 13, no. 2, Oct. 2018, pp. 25-36, https://so04.tci-thaijo.org/index.php/tourismtaat/article/view/151043.