Phanikumar CV, Maitra B. Willingness-to-pay and preference heterogeneity for rural bus attributes. J Transp Eng A-Syst. 2007 Jan;133(1).
Garcia-Esteve L, Torres A, Navarro P, Aguado J, Ascaso C. Maternidad the planned y psicomorbilidad: un riesgo evitable / Unplanned pregnancy and psychological morbidity: an avoidable risk. Fac Med Barc. 2005 Jul;32(3):111-8.