@article{ref1,
title="Physical activity of adolescents",
journal="Arztliche Jugendkunde",
year="1987",
author="Schlegel, V. and Heinze, I. and Gessner, B. and Seidel, A.",
volume="78",
number="2",
pages="108-117",
abstract="<p>[Abstract unavailable]</p><p>Language: de</p>",
language="de",
issn="0001-9518",
doi="",
url="http://dx.doi.org/"
}