Artikel 19

1. This Convention does not affect the rights and undertakings derived from international multilateral instruments concerning special matters.
2. The Parties to the Convention may conclude bilateral or multilateral agreements with one another on the matters dealt with in this Convention, for purposes of supplementing or strengthening its provisions or facilitating the application of the principles embodied in it or, without prejudice to the objectives and principles of this Convention, submit themselves to rules on this matter within the framework of a special system which is binding at the moment of the opening for signature of this Convention.
3. If two or more Parties have already concluded an agreement or treaty in respect of a subject which is dealt with in this Convention or otherwise have established their relations in respect of that subject, they shall be entitled to apply that agreement or treaty or to regulate these relations accordingly, in lieu of the present Convention.