@article{ref1,
title="Sleep variety: physiology, psychology and epidemiology",
journal="Journal of sleep research",
year="2010",
author="Dijk, Derk‐jan",
volume="19",
number="3",
pages="381-383",
abstract="<p>[Abstract unavailable]</p>",
language="",
issn="0962-1105",
doi="10.1111/j.1365-2869.2010.00879.x",
url="http://dx.doi.org/10.1111/j.1365-2869.2010.00879.x"
}