@article{ref1,
title="Two Studies in Airport Congestion",
journal="OR: Operational research quarterly (1953)",
year="1958",
author="Friend, J. K.",
volume="9",
number="3",
pages="234-253",
abstract="<p>[Abstract unavailable]</p>",
language="",
issn="1473-2858",
doi="",
url="http://dx.doi.org/"
}