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
Mansfield CA, Pattanayak SK, McDow W, MacDonald R, Halpin P. Shades of green: measuring the value of urban forests in the housing market. J Forest Econ. 2005 Dec;11(3):177-99. doi: 10.1016/j.jfe.2005.08.002
Glass RL, Rothman KJ, Espinal F, Velez H, Smith NJ. Prevalence of human dental caries and water-borne trace metals. Arch Oral Biol. 1973 Sep;18(9):1099-104. doi: 10.1016/0003-9969(73)90083-6