Zengrui, T., G. Buitrago, and H. Wahdan. “Perceived Happiness and Economic Development：Easterlin Paradox and the Latin American Case”. Journal of Research in Business, Economics and Management, Vol. 10, no. 2, Feb. 2018, pp. 1851-9, http://scitecresearch.com/journals/index.php/jrbem/article/view/1378.