@article{ref1,
title="A pictorial representation of confounding in epidemiologic studies",
journal="Journal of chronic diseases",
year="1975",
author="Rothman, Kenneth J.",
volume="28",
number="2",
pages="101-108",
abstract="<p>[Abstract unavailable]</p><p>Language: en</p>",
language="en",
issn="0021-9681",
doi="",
url="http://dx.doi.org/"
}