2. similar market shares; 3. high legal or economic barriers to entry; 4. vertical integration with collective refusal to supply; 5. lack of countervailing buying power; 6. lack of potential competition. Article 98 (conduct of the Agency in determining significant market power) In determining significant market power and using the criteria referred to in Articles 96 and 97 of this Act, the Agency shall act in accordance with EU legislation and adhere consistently to Commission guidelines governing market analysis and the determination of significant market power in the area of electronic communications networks and services. In doing so, the Agency shall cooperate with the body responsible for the protection of competition. Article 99 (determination of relevant markets) (1) The Agency must, in the area of the provision and implementation of electronic communications in accordance with the principles of competition law, with consistent adherence to each and any Commission recommendation on the relevant markets of products and services in the area of electronic communications and to the guidelines referred to in the previous Article of this Act, determine the product, service and geographical markets relevant to conditions in the country in its analysis of an individual relevant market. In doing so, the Agency shall cooperate with the body responsible for the protection of competition. (2) Where, by means of the decision referred to in Article 101 of this Act, the Agency intends to regulate a market that is not mentioned in a recommendation referred to in the preceding paragraph, it must first carry out a test of three criteria, which are cumulative, in accordance with this recommendation for such a market: 1. the presence of high and constant barriers to entry of a structural, legal or regulatory nature; 2. the structure of the market, which tends towards inefficient competition within a suitable timeframe; 3. the fact that competition legislation does not suffice to ensure an adequate market response. (3) In the cumulative compliance with the criteria referred to in the preceding paragraph, the Agency must, for regulation of such a relevant market, hold a public consultation in accordance with Article 204, engage in cooperation in accordance with Article 214, and consult other regulatory authorities, the Commission and BEREC in accordance with Articles 209, 210 and 212 of this Act. Article 100 (analysis of relevant markets) (1) The Agency must, at regular intervals of time, analyse the markets referred to in the first paragraph of the previous Article. In doing so it shall, where it assesses such a course of action appropriate under the circumstances, work professionally with the body responsible for the protection of competition in accordance with Article 214 of this Act. (2) The Agency must conduct the analysis referred to in the preceding paragraph no later than three years after the adoption of the previous measure relating to the relevant market. This