@article{ref1,
title="Contemporary population densities and human health",
journal="Nature",
year="1973",
author="Factor, R. M. and Waldron, I.",
volume="243",
number="5407",
pages="381-384",
abstract="<p>[Abstract unavailable]</p><p>Language: en</p>",
language="en",
issn="0028-0836",
doi="",
url="http://dx.doi.org/"
}