I think the following links can help:

- [http://www.user-agents.org/](https://web.archive.org/web/20150218042806/http://www.user-agents.org/) (archived page)
- https://en.wikipedia.org/wiki/User_agent#Format_for_automated_agents_(bots)
- https://www.rfc-editor.org/rfc/rfc1945#section-10.15