@article{ref1,
title="Performance of retarded children on a liquid conservation task: protocol objectivity and visual screening",
journal="American journal of mental deficiency",
year="1972",
author="Langley, John Desmond and Drew, C. J.",
volume="76",
number="6",
pages="729-732",
abstract="<p>[Abstract unavailable]</p><p>Language: en</p>",
language="en",
issn="0002-9351",
doi="",
url="http://dx.doi.org/"
}