Author: Tim_Porter Format: MarkdownItexUpdated the link to his webpage
<a href="https://ncatlab.org/nlab/revision/diff/David+Spivak/3">diff</a>, <a href="https://ncatlab.org/nlab/revision/David+Spivak/3">v3</a>, <a href="https://ncatlab.org/nlab/show/David+Spivak">current</a>