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
Bray JW, Davis KL, Graver L, Schroeder D, Buck JA, Dilonardo J, Vandivort R. Mental health and substance abuse treatment utilization among individuals served by multiple public agencies in 3 states. J Behav Health Serv Res. 2005 Jan 1;32(3):282-93.