@article{ref1,
title="Biological age in adulthood: comparison of active and inactive U.S. males",
journal="Human biology; an international record of research",
year="1980",
author="Borkan, G. A. and Norris, A. H.",
volume="52",
number="4",
pages="787-802",
abstract="<p>[Abstract unavailable]</p><p>Language: en</p>",
language="en",
issn="0018-7143",
doi="",
url="http://dx.doi.org/"
}