See the full Copyright Guide for more information.
The Scholarly Publishing and Academic Resources Coalition (SPARC) is a great source of information on author's rights, including this Author's Addendum. This addendum is a legal instrument that modifies the publisher's agreement and allows authors to keep key rights.
For example: To secure sufficient rights to deposit the work in the TXST Digital Collections Repository and to reuse your own work, authors could modify the language of the standard publishing agreement as follows:
For information or questions, contact Stephanie Towery (Copyright Officer): copyrightoffice@txstate.edu