to vacate such radio-frequency spectrum taking into account the use to be given thereto as well its implications and technical requirements. 8. In the case mentioned in paragraph 5 of this article, the period set forth in the preceding paragraph shall, save in duly justified exceptional circumstances, be no less than six months after a written notice is given. 9. The suspension, revocation or amendment of a radio-frequency spectrum licence and the vacation of radio-frequency spectrum pursuant to the article as well as any compensation payable in relation thereto shall be subject to paragraph 4 of article 19. CHAPTER XIV NUMBERING AND DOMAINS Article 66 National numbering plan 1. The Authority shall: a) Within two years from the date of entry into force of the present Decree-law, prepare, issue and publish on its website, and thereafter periodically review, a national numbering plan for the use, allocation and assignment of numbers and number series; and b) Establish procedures, rules and guidelines relating to the allocation, assignment and use of numbers and number series in accordance with such national numbering plan. The Authority shall carry out allocation and assignment of numbers in accordance with the national numbering plan and procedures, rules and guidelines established pursuant to this article. 2. 3. The issuance and review of the national numbering plan pursuant to this article shall be subject to paragraph 4 of article 19. Section 67 Numbering management 1. The Authority shall have the exclusive right to manage, allocate and assign numbers for telecommunications in Timor-Leste. 2. The Authority shall ensure that numbers are managed and used in a manner that: a) Is objective, transparent, non-discriminatory and proportionate; b) Relies, where reasonable, on industry standards and self-regulation; c) Promotes the efficient use of numbers;