@article{ref1,
title="Active transportation surveillance: United States, 1999-2012",
journal="American journal of public health",
year="2016",
author="",
volume="106",
number="3",
pages="e1-4",
abstract="<p>[Abstract unavailable]</p> <p>Language: en</p>",
language="en",
issn="0090-0036",
doi="10.2105/AJPH.2016.303102",
url="http://dx.doi.org/10.2105/AJPH.2016.303102"
}