Author: Tim_Porter Format: MarkdownItexAdded in an explicit reference to Gabriel and Zisman.
<a href="https://ncatlab.org/nlab/revision/diff/category+of+fractions/14">diff</a>, <a href="https://ncatlab.org/nlab/revision/category+of+fractions/14">v14</a>, <a href="https://ncatlab.org/nlab/show/category+of+fractions">current</a>
Added in an explicit reference to Gabriel and Zisman.