@article{ref1,
title="Medical certificates exempting motorcyclists from wearing helmets: an Australian experience",
journal="Journal of traffic medicine",
year="1992",
author="Simpson, D. A. and Brazenor, G. A. and Dan, N. G. and McLean, A. J.",
volume="20",
number="4",
pages="171-176",
abstract="<p>[Abstract unavailable]</p>",
language="en",
issn="0345-5564",
doi="",
url="http://dx.doi.org/"
}