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
Hong J, Novick D, Montgomery W, Aguado J, Dueñas H, Peng X, Haro JM. Should unexplained painful physical symptoms be considered within the spectrum of depressive symptoms? Clin Pract Epidemiol Ment Health. 2015 Mar 31;11:130-9. doi: 10.2174/1745017901511010130
Britt (DiBenedetti) DM, Collins FL, Cohen LM. Cigarette smoking and chewing gum use among college students. J Appl Biobehav Res. 2007 Jun 4;4(2):85-90. doi: 10.1111/j.1751-9861.1999.tb00057.x