@article{ref1,
title="Higher oxides of nitrogen as an impurity in nitrous oxide",
journal="British journal of anaesthesia",
year="1967",
author="",
volume="39",
number="5",
pages="343-344",
abstract="<p>[Abstract unavailable]</p><p>Language: en</p>",
language="en",
issn="0007-0912",
doi="",
url="http://dx.doi.org/"
}