-6Article 14 1 The Parties undertake to recognise that every person belonging to a national minority has the right to learn his or her minority language. 2 In areas inhabited by persons belonging to national minorities traditionally or in substantial numbers, if there is sufficient demand, the Parties shall endeavour to ensure, as far as possible and within the framework of their education systems, that persons belonging to those minorities have adequate opportunities for being taught the minority language or for receiving instruction in this language. 3 Paragraph 2 of this article shall be implemented without prejudice to the learning of the official language or the teaching in this language. Article 15 The Parties shall create the conditions necessary for the effective participation of persons belonging to national minorities in cultural, social and economic life and in public affairs, in particular those affecting them. Article 16 The Parties shall refrain from measures which alter the proportions of the population in areas inhabited by persons belonging to national minorities and are aimed at restricting the rights and freedoms flowing from the principles enshrined in the present framework Convention. Article 17 1 The Parties undertake not to interfere with the right of persons belonging to national minorities to establish and maintain free and peaceful contacts across frontiers with persons lawfully staying in other States, in particular those with whom they share an ethnic, cultural, linguistic or religious identity, or a common cultural heritage. 2 The Parties undertake not to interfere with the right of persons belonging to national minorities to participate in the activities of non-governmental organisations, both at the national and international levels. Article 18 1 The Parties shall endeavour to conclude, where necessary, bilateral and multilateral agreements with other States, in particular neighbouring States, in order to ensure the protection of persons belonging to the national minorities concerned. 2 Where relevant, the Parties shall take measures to encourage transfrontier co-operation. Article 19 The Parties undertake to respect and implement the principles enshrined in the present framework Convention making, where necessary, only those limitations, restrictions or derogations which are provided for in international legal instruments, in particular the Convention for the Protection of Human Rights and Fundamental Freedoms, in so far as they are relevant to the rights and freedoms flowing from the said principles.