@article{ref1,
title="Sample Selection In The Estimation Of Air Bag And Seat Belt Effectiveness",
journal="Review of economics and statistics",
year="2001",
author="Steven D. Levitt,  and Jack Porter, ",
volume="83",
number="4",
pages="603-615",
abstract="<p>[Abstract unavailable]</p>",
language="",
issn="0034-6535",
doi="",
url="http://dx.doi.org/"
}