Raghunathan K, Layton JB, Ohnuma T, Shaw AD. Observational research using propensity scores. Adv Chronic Kidney Dis. 2016 Nov;23(6):367-72. doi: 10.1053/j.ackd.2016.11.010
Von Scheele BG, Martin RD, Gilsenan AW, Ceberg J, Andrews EB, Masica D, Alvegård T. The European postmarketing adult osteosarcoma surveillance study characteristics of patients: a preliminary report. Acta Orthop. 2009;80:67-74.