@article{ref1,
title="Clustering and socially-directed behaviors in a playgroup of 1-yr-old boys",
journal="Journal of child psychology and psychiatry",
year="1976",
author="Mueller, E. and Rich, A.",
volume="17",
number="4",
pages="315-322",
abstract="<p>[Abstract unavailable]</p><p>Language: en</p>",
language="en",
issn="0021-9630",
doi="",
url="http://dx.doi.org/"
}