1. The convention does not affect any international instrument to which Contracting States are Parties and which contains provisions on matters governed by the Convention, unless a contrary declaration is made by the States parties to such instrument.N.I.
2. Any Contracting State may enter into agreements with one or more other Contracting States, with a view to improving the application of the Convention in their mutual relations. These agreements may derogate only from the provisions of Articles 14 to 16 and 18 to 21. The States which have concluded such an agreement shall transmit a copy to the depositary of the Convention.N.I.