@article{ref1,
title="Circadian variability in vigilance performance",
journal="Aerospace medicine",
year="1968",
author="Frazier, T. W. and Rummel, J. A. and Lipscomb, H. S.",
volume="39",
number="4",
pages="383-385",
abstract="<p>[Abstract unavailable]</p><p>Language: en</p>",
language="en",
issn="0001-9402",
doi="",
url="http://dx.doi.org/"
}