@article{ref1,
title="Methodological considerations of visual workloads of helicopter pilots",
journal="Human factors",
year="1979",
author="Simmons, R. R.",
volume="21",
number="3",
pages="353-367",
abstract="Abstract unavailable.",
language="",
issn="0018-7208",
doi="",
url="http://dx.doi.org/"
}