@article{ref1,
title="Ultradian rhythms in extended performance",
journal="Aerospace medicine",
year="1974",
author="Orr, W. C. and Hoffman, H. J. and Hegge, F. W.",
volume="45",
number="9",
pages="995-1000",
abstract="<p>[Abstract unavailable]</p><p>Language: en</p>",
language="en",
issn="0001-9402",
doi="",
url="http://dx.doi.org/"
}