@article{ref1,
title="Advances in cluster headache",
journal="Neurologic clinics",
year="1990",
author="Mathew, Ninan T.",
volume="8",
number="4",
pages="867-890",
abstract="<p>[Abstract unavailable]</p>",
language="en",
issn="0733-8619",
doi="",
url="http://dx.doi.org/"
}