@article{ref1,
title="Performance changes during the sustained operation of a complex psychomotor task",
journal="Ergonomics",
year="1970",
author="Ellingstad, Vernon S. and Heimstra, Norman W.",
volume="13",
number="6",
pages="693-705",
abstract="<p>[Abstract unavailable]</p> <p>Language: en</p>",
language="en",
issn="0014-0139",
doi="",
url="http://dx.doi.org/"
}