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
Scotland GS, Philip S, Fleming AD, Goatman KA, Sharp PF, McNamee P, Fonseca S, Prescott G, Olson JA. Manual versus automated: the diabetic retinopathy screening debate. OTE. 2008 Jan 1;4(2):14-6.