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
Wallner (MacLeod) S, Kendall P, Hillers V, Bradshaw E, Medeiros LC. Online continuing education course enhances nutrition and health professionals' knowledge of food safety issues of high-risk populations. J Am Diet Assoc. 2007 Aug;107(8):1333-8. doi: 10.1016/j.jada.2007.05.014