Untangling the concepts of disability, frailty, and comorbidity: implications for improved targeting and care.
Fried LP, Ferrucci L, Darer J, Williamson JD, Anderson G. Untangling the concepts of disability, frailty, and comorbidity: implications for improved targeting and care. J Gerontol A Biol Sci Med Sci. 2004 Mar; 59(3):255-63.