Article 12 Any Contracting Party may at any time, by notification addressed to the Secretary-General of the United Nations, extend the application of the present Convention to all or any of the territories for the conduct of whose foreign relations that Contracting Party is responsible. Article 13 On the day when the first twenty instruments of ratification or accession have been deposited, the Secretary-General shall draw up a proces-verbal and transmit a copy of it to each Member of the United Nations and to each of the non-member States contemplated in Article 11. The present Convention shall come into force on the ninetieth day following the date of deposit of the twentieth instrument of ratification or accession. Any ratification or accession effected subsequent to the latter date shall become effective on the ninetieth day following the deposit of the instrument of ratification or accession. Article 14 The present Convention shall remain in effect for a period of ten years as from the date of its coming into force. It shall thereafter remain in force for successive periods of five years for such Contracting Parties as have not denounced it at least six months before the expiration of the current period. Denunciation shall be effected by a written notification addressed to the Secretary-General of the United Nations. Article 15 If, as a result of denunciations, the number of Parties to the present Convention should become less than sixteen, the Convention shall cease to be in force as from the date on which the last of these denunciations shall become effective. Article 16 A request for the revision of the present Convention may be made at any time by any Contracting Party by means of a notification in writing addressed to the Secretary-General. The General Assembly shall decide upon the steps, if any, to be taken in respect of such request. Article 17 The Secretary-General of the United Nations shall notify all Members of the United Nations and the non-member States contemplated in Article 11 of the following: