@article{Freedman2013,
author = {Freedman, V.A. and Spillman, B.C. and Andreski, P.M. and Cornman, J.C. and Crimmins, E.M. and Kramarow, E. and Lubitz, J.},
title= {Trends in Late-Life Activity Limitations in the United States: An Update From Five National Surveys},
year = {2013},
doi = {10.1007/s13524-012-0167-z},
journal = {Demography},
volume = {50},
number = {2},
pages = {661--671},
}