@article{ref1,
title="Treatment-resistant depression: Definition and treatment approaches",
journal="Journal of clinical psychiatry",
year="1990",
author="Nierenberg, Andrew A. and Amsterdam, Jay D.",
volume="51",
number="6, Suppl",
pages="39-47",
abstract="<p>[Abstract unavailable]</p>",
language="en",
issn="0160-6689",
doi="",
url="http://dx.doi.org/"
}