Khon, S., and U. Seenprachawong. “The Public Demand for a Dengue Fever Vaccine: A Contingent Valuation Survey in Phnom Penh, Cambodia”. International Journal of Economics and Financial Issues, vol. 10, no. 6, Nov. 2020, pp. 129-38, https://www.econjournals.com/index.php/ijefi/article/view/10426.