1. Table 3. Projections of the Population by Sex and Selected Age Groups for the United States: 2015 to 2060;Census Bureau,2014
2. The intensity and variation of surgical care at the end of life: a retrospective cohort study;Kwok;Lancet,2011
3. Redefining geriatric preoperative assessment using frailty, disability and co-morbidity;Robinson;Ann Surg,2009
4. Frailty in elderly people;Clegg;Lancet,2013
5. Frailty in older adults: evidence for a phenotype;Fried;J Gerontol A Biol Sci Med Sci,2001