except in the cases of use of an individually assigned scarce resource. Article 69. Public electronic communications shall be implemented by sole traders and by legal persons. Article 70. Electronic communications shall be implemented at all points within the national territory, unless an authorization for use of an individually assigned scarce resource or the general requirements for performance of the particular activity designate a limited territorial range. Article 71. (1) (Redesignated from Article 71 and amended, SG No. 105/2011, effective 29.12.2011) An authorization for use of an individually assigned scarce resource shall be applicable for an initial period of up to twenty years. The period of the authorization shall be extended according to the procedure established by Article 114 (2) herein. (2) (New, SG No. 105/2011, effective 29.12.2011) In determining the initial period referred to in Paragraph (1), the Commission shall take account of the service concerned and the objectives pursued, and shall also allow for a period for investment amortization. Article 72. (1) The networks and/or services, over which public electronic communications are implemented in compliance with general requirements, shall be indicated in a list adopted by the Commission after a public consultation under Article 36 herein. The said decision of the Commission together with the list shall be promulgated in the State Gazette. (2) The List referred to in Paragraph (1) shall be modified on the initiative of the Commission or on a proposal by an interested party after a public consultation under Article 36 herein. Section II Implementation of Electronic Communications in Compliance with General Requirements Article 73. (1) (Amended, SG No. 17/2009, SG No. 105/2011, effective 29.12.2011) Any undertaking, which has submitted a notification on implementation of public electronic communications under Article 66 herein, shall comply with general requirements determined depending on the type of electronic communications network and/or service. The general requirements shall be adopted by decision of the Commission respecting the principles of transparency, non-discrimination and proportionality. (2) (Amended, SG No. 17/2009) The decision referred to in Paragraph (1) shall be adopted after conduct of a public consultation under Article 36 herein and shall be promulgated in the State Gazette. (3) (Amended, SG No. 17/2009) Depending on the type of electronic communications network and/or service, the applicable general requirements, as approved by the decision referred to in Paragraph (1), may contain all or some of the following requirements: 1. to negotiate and to provide access to and interconnection of the network of the undertaking with the networks of other undertakings implementing electronic communications, including: (a) to ensure interoperability of the services of the undertaking with the services of the other undertakings; (b) to maintain the integrity and to guarantee the security of the network of the undertaking; (c) (new, SG No. 105/2011, effective 29.12.2011) to ensure protection of the public network against unauthorized access to personal data; (d) (renumbered from Littera (c), SG No. 105/2011, effective 29.12.2011) if possible, to provide shared use of premises and co-location of premises and facilities of the network of the undertaking to the other undertakings providing public electronic communications networks and/or services; (e) (new, SG No. 105/2011, effective 29.12.2011) to create conditions to prevent electromagnetic interference between electronic communications networks and/or services;