@article{ref1,
title="The Higher Structural Phases of Concept Formation of Children",
journal="Journal of psychology, The",
year="1940",
author="Welch, Livingston and Long, Louis",
volume="9",
number="1",
pages="59-95",
abstract="<p>[Abstract unavailable]</p>",
language="",
issn="0022-3980",
doi="10.1080/00223980.1940.9917678",
url="http://dx.doi.org/10.1080/00223980.1940.9917678"
}