@article{ref1,
title="Night legibility distances of highway signs",
journal="Highway Research Board bulletin",
year="1958",
author="Allen, Terrence M.",
volume="191",
number="",
pages="33-40",
abstract="<p>[Abstract unavailable]</p>",
language="",
issn="0073-2206",
doi="",
url="http://dx.doi.org/"
}