The National Institute of Child Health and Human Development Early Child Care Research Network, McLeod LD. Psychosocial and lifestyle factors associated with early-onset persistent and late-onset asthma. J Child Health Care. 2010;39(3):185-98.
Phanikumar CV, Maitra B. Willingness-to-pay and preference heterogeneity for rural bus attributes. J Transp Eng A-Syst. 2007 Jan;133(1).