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1. The Contracting Parties may not conclude bilateral or multilateral agreements with one another on the matters dealt with in this Convention, except in order to supplement its provisions or facilitate application of the principles embodied in it.
2. However, should two or more Contracting Parties establish or have already established their relations in this matter on the basis of uniform legislation or a special system of their own, providing for more extensive obligations, they shall be entitled to regulate those relations accordingly notwithstanding the provisions of this Convention.
3. Contracting Parties ceasing in accordance with paragraph 2 of this Article to apply the terms of this Convention to their mutual relations in this matter shall notify the Secretary General of the Council of Europe to that effect.