@article{ref1,
title="The effects of symbol frequency in legibility testing",
journal="Human factors",
year="1967",
author="Bell, G. L.",
volume="9",
number="5",
pages="471-478",
abstract="<p>[Abstract unavailable]</p><p>Language: en</p>",
language="en",
issn="0018-7208",
doi="",
url="http://dx.doi.org/"
}