@article{ref1,
title="Learning to use a lever",
journal="Child development",
year="1972",
author="Koslowski, B. and Bruner, J. S.",
volume="43",
number="3",
pages="790-799",
abstract="<p>[Abstract unavailable]</p><p>Language: en</p>",
language="en",
issn="0009-3920",
doi="",
url="http://dx.doi.org/"
}