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
Watts (Wideman) K, McAvinchey G, Quiroz R. Language services in survey research. ATA Chronicle. 2002 Jul;31(7):36-7.