@article{ref1,
title="Studies of pilot performance: ii. evaluation of performance during low altitude flight in helicopters",
journal="Aerospace medicine",
year="1968",
author="Billings, C. E. and Eggspuehler, J. J. and Gerke, R. J. and Chase, R. C.",
volume="39",
number="1",
pages="19-31",
abstract="<p>[Abstract unavailable]</p> <p>Language: en</p>",
language="en",
issn="0001-9402",
doi="",
url="http://dx.doi.org/"
}