@article{ref1,
title="Play disturbances at pre-school age as precursors to learning difficulties of children and adolescents (author's transl)",
journal="Acta paedopsychiatrica",
year="1974",
author="Nissen, G.",
volume="40",
number="6",
pages="214-220",
abstract="<p>[Abstract unavailable]</p><p>Language: de</p>",
language="de",
issn="0001-6586",
doi="",
url="http://dx.doi.org/"
}