@article{ref1,
title="An extract of a letter of the learned Dr. Gothofredus Guil. Leibnitz, concerning the principle of exactness in the portable watches of his invention",
journal="Philosophical transactions of the Royal Society of London (1665)",
year="1675",
author="Leibnitz, Gothofredus Guilelmus",
volume="10",
number="113",
pages="285-288",
abstract="<p>[Abstract unavailable]</p>",
language="",
issn="0370-2316",
doi="",
url="http://dx.doi.org/"
}