Mitchell S.L, Kiely D.K, Lipsitz L.A.  1997.  The risk factors and impact on survival of feeding tube placement in nursing home residents with severe cognitive impairment.. Archives of Internal Medicine. 157(3):327-32.

Perls T.T, Morris J.N, Ooi W.L, Lipsitz L.A.  1993.  The relationship between age, gender and cognitive performance in the very old: the effect of selective survival. Journal of the American Geriatrics Society. 41(11):1193-201.