Fleming A, Goatman KA, Sharp PF, Styles CJ, Wikes WN, Olson JA. A large scale validation of automated grading. Eur J Ophthalmol. 2009 May 1;19(3):504.
Phanikumar CV, Maitra B. Willingness-to-pay and preference heterogeneity for rural bus attributes. J Transp Eng A-Syst. 2007 Jan;133(1).