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
Beach RH, Poulos C, Pattanayak SK. Farm economics of bird flu. Revue Canadienne D'agroeconomie. 2007 Dec 1;55(4):471-83.