Merrill RM, Kelley TA, Cox E, Layman AB, Layton BJ, Lindsay R. Factors and barriers influencing influenza vaccination among students at Brigham Young University. Med Sci Monit. 2010 Feb;16(2):PH29-34.
Derby CA, Araujo AB, Johannes CB, Feldman HA, McKinlay JB. Measurement of erectile dysfunction in population-based studies: the use of a single question self-assessment in the Massachusetts Male Aging Study. Int J Impot Res. 2000 Aug 1;12(4):197-204.