Article 47 1. In the application of the provisions of the present Convention, the receiving State shall not discriminate as between States. 2. However, discrimination shall not be regarded as taking place: (a) Where the receiving State applies any of the provisions of the present Convention restrictively because of a restrictive application of that provision to its mission in the sending State; (b) Where by custom or agreement States extend to each other more favourable treatment than is required by the provisions of the present Convention. Article 48 The present Convention shall be open for signature by all States Members of the United Nations or of any of the specialized agencies Parties to the Statute of the International Court of Justice, and by any other State invited by the General Assembly of the United Nations to become a Party to the Convention, as follows: until 31 October 1961 at the Federal Ministry for Foreign Affairs of Austria and subsequently, until 31 March 1962, at the United Nations Headquarters in New York. Article 49 The present Convention is subject to ratification. The instruments of ratification shall be deposited with the Secretary-General of the United Nations. Article 50 The present Convention shall remain open for accession by any State belonging to any of the four categories mentioned in article 48. The instruments of accession shall be deposited with the SecretaryGeneral of the United Nations. Article 51 1. The present Convention shall enter into force on the thirtieth day following the date of deposit of the twenty-second instrument of ratification or accession with the Secretary-General of the United Nations. 2. For each State ratifying or acceding to the Convention after the deposit of the twenty-second instrument of ratification or accession, the Convention shall enter into force on the thirtieth day after deposit by such State of its instrument of ratification or accession. Article 52 The Secretary-General of the United Nations shall inform all States belonging to any of the four categories mentioned in article 48: 15