@article{ref1,
title="Places to walk: convenience and regular physical activity",
journal="American journal of public health",
year="2003",
author="Chowdhury, Pranesh P. and Martin, Linda M. and Powell, Kenneth E.",
volume="93",
number="9",
pages="1519-1521",
abstract="Abstract unavailable",
language="",
issn="0090-0036",
doi="",
url="http://dx.doi.org/"
}