1 Feldman HA, Goldstein I, Hatzichristou DG, Krane RJ, McKinlay JB. Impotence and its medical and psychosocial correlates: results of the Massachusetts Male Aging Study. J Urol. 1994;151(1):54–61.
2 Earle CM, Stuckey BG. Biochemical screening in the assessment of erectile dysfunction: what tests decide future therapy? Urology. 2003;62(4):727–31.
3 Araujo AB, Esche GR, Kupelian V, O’Donnell AB, Travison TG, Williams RE, et al. Prevalence of symptomatic androgen deficiency in men. J Clin Endocrinol Metab. 2007;92(11):4241–7.
4 Andersen KV, Bovim G. Impotence and nerve entrapment in long distance amateur cyclists. Acta Neurol Scand. 1997;95(4):233–40.
5 Marceau L, Kleinman K, Goldstein I, McKinlay J. Does bicycling contribute to the risk of erectile dysfunction? Results from the Massachusetts Male Aging Study (MMAS). Int J Impot Res. 2001;13(5):298–302.
6 Kim KK, Kim DG, Ku YH, Lee YJ, Kim WC, Kim OJ, et al. Bilateral cerebral hemispheric infarction associated with sildenafil citrate (Viagra) use. Eur J Neurol. 2008;15(3):306–8.
7 Jackson G, Arver S, Banks I, Stecher VJ. Counterfeit phosphodiesterase type 5 inhibitors pose significant safety risks. Int J Clin Pract. 2010;64(4):497–504.