@article{Greenwell1997,
author = {Greenwell, L. and Bengtson, V.L.},
title= {Geographic distance and contact between middle-aged children and their parents: The effects of social class over 20 years},
year = {1997},
doi = {10.1093/geronb/52B.1.S13},
volume = {52},
number = {1},
pages = {S13--S26},
}