@article{ref1,
title="The Playground as a Factor in School Hygiene",
journal="Psychol Clin",
year="1909",
author="Johnson, George E.",
volume="3",
number="1",
pages="14-20",
abstract="<p>[Abstract unavailable]</p><p>Language: en</p>",
language="en",
issn="",
doi="",
url="http://dx.doi.org/"
}