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
Ferguson JE3rd, Goyal RK, Raynor MC, Nielsen ME, Pruthi RS, Brown PM, Wallen EM. Cost analysis of robot-assisted laparoscopic versus hand-assisted laparoscopic partial nephrectomy. J Endourol. 2012 Aug;26(8):1030-7.
Niaura R, Britt DM, Shadel WG, Goldstein M, Abrams D, Brown R. Symptoms of depression and survival experience among three samples of smokers trying to quit. Psychol Addict Behav. 2001 Mar 1;15(1):13-7.