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
Saigi N, Espelt A, Folch C, Sarasa-Renedo A, Castellano Y, Majo X, Merono M, Brugal MT, Casabona J, REDAN Group. Differences in illegal drug consumption between native and immigrants in a large sample of injected drug users in Catalonia (Spain). Adicciones. 2014;26(1):69-76. doi: 10.20882/adicciones.136