require, in consideration for a sharing request from another service provider, that such service provider make available for sharing a substantial number of cell sites of its own, whether installed or to be installed, by entering into a bilateral framework agreement regulating the relations between the parties regarding site sharing. 12. For the purposes of this article, an “owner service provider” shall refer to a service provider having the ownership, lease or other right to use a cell site. Article 41 Access 1. The Authority may impose on service providers with significant market power in a particular telecommunications market obligations to respond to reasonable access requests made in writing in situations where the denial of access, or the setting of unreasonable conditions that have an effect equivalent to a denial of access, would hinder the emergence of a sustainable competitive retail market or harm the interests of end users. 2. The Authority may request that the agreements pursuant to the preceding paragraph provide for: a) Access to specified network resources and/or facilities; b) Specified services on a wholesale basis for resale by third parties; c) Co-location or other forms of associated facilities sharing; and d) 3. Access to operational support systems or similar software systems necessary to ensure the effective provision of the forms of access referred to in the preceding paragraphs. In considering matters related to this article, the Authority shall take into account: a) The relevant capacity, technical and/or operational constraints; b) The technical and economic viability of using or installing alternative facilities or services; c) Any relevant intellectual property rights; and d) The objective provided for in article 2 of the present Decree-Law. 4. The Authority shall not, before a period of two years has elapsed from the date of entry into force of the present Decree-Law, impose any obligation on any service provider to provide: a) National roaming services; or