Phanikumar CV, Maitra B. Modeling willingness-to-pay values for rural bus attributes under different trip purposes. JTRF. 2006;45(2):31-44. doi: 10.22004/ag.econ.206787
Cann CI, Fried MP, Rothman KJ. Epidemiology of squamous-cell cancer of the head and neck. Otolaryngol Clin N Am. 1985 Aug 1;18(3):367-88.
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