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
Cates SC, Kosa KM, Karns S, Godwin SL, Speller-Henderson L, Harrison R, Ann Draughon F. Food safety knowledge and practices among older adults: identifying causes and solutions for risky behaviors. J Nutr Elder. 2009 Apr;28(2):112-26. doi: 10.1080/01639360902949986