Signed in Brussels on November 23, 1970, and entry into force on January 1, 1973, the Additional Protocol is an extensive treaty to the Ankara Agreement, aiming to further extend the Association within the context of an enlarged Union. It strengthens customs cooperation, providing, among other things, for the mutual acceptance of certain movement certificates and information sheets. The Protocol is an integral part of the Ankara Agreement.
https://eur-lex.europa.eu/legal-content/IT/TXT/PDF/?uri=CELEX:22005A0930(01