@article{ref1,
title="Notes on two multiple-variable spot maps",
journal="Social forces",
year="1928",
author="Schmid, Calvin F.",
volume="6",
number="3",
pages="378-382",
abstract="<p>[Abstract unavailable]</p>",
language="en",
issn="0037-7732",
doi="10.2307/3004856",
url="http://dx.doi.org/10.2307/3004856"
}