Rousu M, Kosa K. Allowing options in experimental auctions. Appl Econ Lett. 2005;12(13):817-21. doi: 10.1080/13504850500193059
Zhao JH, Brunner EJ, Kumari M, Singh-Manoux A, Hawe E, Talmud PJ, Marmot MG, Humphries SE. APOE polymorphism, socioeconomic status and cognitive function in mid-life--the Whitehall II longitudinal study. Soc Psychiatry Psychiatr Epidemiol. 2005;40(7):557-63.