Author: DavidRoberts Format: MarkdownItexAdded mention that this rule corresponds to having diagonals.
<a href="https://ncatlab.org/nlab/revision/diff/contraction+rule/3">diff</a>, <a href="https://ncatlab.org/nlab/revision/contraction+rule/3">v3</a>, <a href="https://ncatlab.org/nlab/show/contraction+rule">current</a>
Added mention that this rule corresponds to having diagonals.