[ownedbycats]

As defined in Preferences > Look & Feel > Book Details > Create rules to convert identifiers to links

Here are my own.

ao3 | Archive of Our Own | https://archiveofourown.org/works/{id}
ffnet | FanFiction.net | https://www.fanfiction.net/s/{id}/1/
lccn | Library of Congress | https://lccn.loc.gov/{id}
iarchive | Internet Archive | https://archive.org/details/{id}
ol | Open Library | https://openlibrary.org/works/{id}/
gutenberg | Project Gutenberg | http://www.gutenberg.org/ebooks/{id}