@article{ref1,
title="Scale Factors in the Management of Coal Mines",
journal="OR: Operational research quarterly (1953)",
year="1955",
author="Revans, R. W.",
volume="6",
number="3",
pages="91-107",
abstract="<p>[Abstract unavailable]</p>",
language="",
issn="1473-2858",
doi="",
url="http://dx.doi.org/"
}