Author: Urs Format: MarkdownItexadded some references for the terminology
<a href="https://ncatlab.org/nlab/revision/diff/writhe/4">diff</a>, <a href="https://ncatlab.org/nlab/revision/writhe/4">v4</a>, <a href="https://ncatlab.org/nlab/show/writhe">current</a>