Author: Tim_Porter Format: MarkdownItexUpdated a dead link and added some more information.
<a href="https://ncatlab.org/nlab/revision/diff/Donovan+van+Osdol/2">diff</a>, <a href="https://ncatlab.org/nlab/revision/Donovan+van+Osdol/2">v2</a>, <a href="https://ncatlab.org/nlab/show/Donovan+van+Osdol">current</a>
Updated a dead link and added some more information.