@article{ref1,
title="Posttraumatic headache",
journal="Neurology",
year="1997",
author="Haas, D. C.",
volume="48",
number="6",
pages="1735-1735",
abstract="<p>[Abstract unavailable]</p><p>Language: en</p>",
language="en",
issn="0028-3878",
doi="",
url="http://dx.doi.org/"
}