447-450. Frey. B. S.. & Stumer, A. (2000). What can economists lean. from happiness research? Journal of Economic Literature. 40, 402-435. Gerson. E. S.. & Woolsey. B. (2009). The history of credit cards. Retrieved from Gilbert, D. T. (2006). Stumbling on happiness. New York: Knopf. Gilbert, a T., & Ebert, J.