Kaplan RC, Heckbert SR, Koepsell TD, Furberg CD, Polak JF, Schoen RE, Psaty BM. Risk factors for hospitalized gastrointestinal bleeding among older persons. Cardiovascular Health Study Investigators. J Am Geriatr Soc. 2001  ;49(2):126-33.

Kaplan RC, Heckbert SR, Koepsell TD, Rosendaal FR, Furberg CD, Cooper LS, Psaty BM. Calcium channel blocker use and gastrointestinal tract bleeding among older adults. Age Ageing. 2002  ;31(3):217-8.