@article{ref1,
title="Circadian rhythm in indices of human performance, physical fitness and stress resistance",
journal="Aerospace medicine",
year="1968",
author="Klein, K. E. and Wegmann, H. M. and Brüner, H.",
volume="39",
number="5",
pages="512-518",
abstract="<p>[Abstract unavailable]</p><p>Language: en</p>",
language="en",
issn="0001-9402",
doi="",
url="http://dx.doi.org/"
}