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
Sorensen HT, Steffensen FH, Sabroe S, Rothman KJ, Gillman MW, Fischer P. Historical cohort study of in utero exposure to uterotonic drugs and cognitive function in young adult life. West J Med. 1999 Jan 1;170(5):260-2.