@article{ref1,
title="Legibility of numbers as a function of contrast and illumination",
journal="Human factors",
year="1967",
author="Williams, C. M.",
volume="9",
number="5",
pages="455-460",
abstract="<p>[Abstract unavailable]</p><p>Language: en</p>",
language="en",
issn="0018-7208",
doi="",
url="http://dx.doi.org/"
}