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
McDonald R, Mead N, Cheraghi-Sohi S, Bower P, Whalley D. Governing the ethical consumer: identity, choice and the primary care medical encounter. Sociol Health Illn. 2007 Apr 1;29(3):430-56.