@article{ref1,
title="Self-administration of abused substances: methods for study. Introduction and implications",
journal="NIDA research monograph",
year="1978",
author="Krasnegor, N. A.",
volume="",
number="20",
pages="1-2",
abstract="<p>[Abstract unavailable]</p><p>Language: en</p>",
language="en",
issn="1046-9516",
doi="",
url="http://dx.doi.org/"
}