@article{ref1,
title="Diurnal variation, task characteristics, and vigilance performance",
journal="Human factors",
year="1987",
author="Matthews, Gerald and Davies, D. R. and Craig, A.",
volume="29",
number="6",
pages="675-684",
abstract="Abstract unavailable.",
language="",
issn="0018-7208",
doi="",
url="http://dx.doi.org/"
}