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Perkins MM, Ball MM, Kemp CL, Hollingsworth C.Perkins MM, et al. Among authors: kemp cl.Gerontologist. 2013 Jun;53(3):495-507. doi: 10.1093/geront/gns124. Epub 2012 Oct 4.Gerontologist. 2013.PMID: 23042689Free PMC article.