How can the right to Open Access publication be asserted in contract agreements?

Many authors modify publisher contracts that restrict their rights to store their publications on a document server by clearly deleting terms such as “exclusive” transfer of “all” rights, as well as other restrictive phrasing. A cover letter should draw attention to the modifications. Alternatively, authors can include an addendum to the publisher’s contract (countersigned by the publisher to be legally valid). The Author’s Addendum from SPARC (The Scholarly Publishing and Academic Resources Coalition) is the most well-known and accepted of these. Example: "I hereby declare that I do not wish to assign the exclusive copyright to (name of publisher) but reserve the right to publish the article in full on an open access platform."