@article{ref1,
title="Play in pre-school centres--I. Play measures and their relation to age, sex and I.Q",
journal="Journal of child psychology and psychiatry",
year="1976",
author="Tizard, B. and Philps, J. and Plewis, I.",
volume="17",
number="4",
pages="251-264",
abstract="<p>[Abstract unavailable]</p><p>Language: en</p>",
language="en",
issn="0021-9630",
doi="",
url="http://dx.doi.org/"
}