9 2. A State Party shall provide in law for proof of the facts establishing entitlement to nationality at birth or the conditions for acquisition of nationality by oral testimony or other appropriate means, in accordance with its national law on evidence where documentary evidence is not available or cannot reasonably be demanded. ARTICLE 12 Documentation of Nationality 1. A State Party shall provide in its national law for the right to a certificate of nationality or other appropriate document that is proof of a person’s nationality and shall define the authorities and procedures to obtain that document. 2. A State Party shall issue to every national on application after satisfaction of the administrative formalities established in national legislation, the documents legally accepted as proof of nationality. 3. A State Party shall take all appropriate measures to ensure that unaccompanied and separated children obtain the documents accepted as proof of nationality, whether of the State where the child is present or, where relevant, another State, which shall be issued in their own names. 4. A State Party shall prohibit all arbitrary acts of cancellation, non-renewal, confiscation or destruction of the documents referred to in this article belonging to any person. 5. When a person holds a document issued by the competent State authorities indicating that he or she is the national of a State, the burden shall be on the institution that asserts that he or she is not a national to prove that the person does not have the nationality to which he or she claims to be entitled. ARTICLE 13 Renunciation of Nationality A State Party shall not prohibit its national from renouncing his or her nationality, unless such renunciation would render the person stateless, in accordance with national law. ARTICLE 14 Loss of nationality If a State Party does not permit multiple nationality, it may provide for the loss of its nationality in case of voluntary acquisition by a national of another nationality.