Wardman M, Chintakayala PK, de Jong G. Values of travel time in Europe: review and meta-analysis. Transp Res Part A Policy Pract. 2016 Dec;94:93-111. doi: 10.1016/j.tra.2016.08.019
Whittington D, Sur D, Cook J, Chatterjee S, Maskery B, Lahiri M, Poulos C, Boral S, Nyamete A, Deen J, Ochiai L, Bhattacharya SK. Rethinking cholera and typhoid vaccination policies for the poor: private demand in Kolkata, India. World Dev. 2009 Feb 1;37(2):399-409.