@article{ref1,
title="Early warning systems: do they work?",
journal="Tropical doctor",
year="1991",
author="Walker, P.",
volume="21",
number="Suppl 1",
pages="5-8",
abstract="<p>[Abstract unavailable]</p> <p>Language: en</p>",
language="en",
issn="0049-4755",
doi="",
url="http://dx.doi.org/"
}