- The Wikidata article for Possession Point says that Skagit Head is an alternate name of Possession Point. However, Skagit Head is listed by MapCarta to refer to Skatchet Head.
- Mark Twain Project Online (marktwinproject.org)
Mark Twain Project Online applies innovative technology to more than four decades’ worth of archival research by expert editors at the Mark Twain Project. It offers unfettered, intuitive access to reliable texts, accurate and exhaustive notes, and the most recently discovered letters and documents.