Wilson MR, Van Houtven CH, Stearns S, Clipp EC. Depression and missed work among informal caregivers of older individuals with dementia. J Fam Econ Issues. 2007;28(4):684-98.
Phanikumar CV, Maitra B. Willingness-to-pay and preference heterogeneity for rural bus attributes. J Transp Eng A-Syst. 2007 Jan;133(1).