@article{ref1,
title="The "Age 60" rule approaching the twenty-first century",
journal="Aviation, space, and environmental medicine",
year="1993",
author="Clarke, W. R.",
volume="64",
number="11",
pages="1059-1059",
abstract="<p>[Abstract unavailable]</p><p>Language: en</p>",
language="en",
issn="0095-6562",
doi="",
url="http://dx.doi.org/"
}