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
Whalley D, Gravelle H, Sibbald B. Effect of the new contract on GPs' working lives and perceptions of quality of care: a longitudinal survey. Br J Gen Pract. 2008 Jan 1;58(546):8-14.
Whalley D, Bojke C, Gravelle H, Sibbald GP. GP job satisfaction in view of contract reform: a national survey. Br J Gen Pract. 2006 Feb 1;56(523):87-92.
Dreyer NA, Loughlin JE, Rothman KJ. Epidemiologic safety surveillance of cellular telephones in the US. Radiat Prot Dosimetry. 1999 Jun;83(1):159-63.