Christensen T, Riis AH, Hatch EE, Wise LA, Nielsen MG, Rothman KJ, Toft Sorensen H, Mikkelsen EM. Costs and efficiency of online and offline recruitment methods: a web-based cohort study. J Med Internet Res. 2017 Mar 1;19(3):e58. doi: 10.2196/jmir.6716
Fleming A, Olson JA, Sharp PF, Goatman KA, Philip S. Response to 'Improved automated screening of diabetic retinopathy' by Carlos M. Oliveira et al. Ophthalmologica. 2012 Jan 1;227(3):173. doi: 10.1159/000334922