prices of services and of the internal transfer prices. (3) The Commission may also impose the obligation under Paragraph (2) where it considers that there exists an opportunity for violation of the prohibition of cross-subsidy. (4) The Commission may, after consultations with the undertaking concerned, specify the format and the accounting methodology to be used in determination of prices. (5) To ensure implementation of the obligations referred to in Paragraphs (2) and (4), the Commission may require that the undertakings providing public electronic communications networks provide accounting records and information including data on revenues received by third parties. (6) The Commission may publish the information received where this would contribute to creating conditions for effective competition, while respecting the requirements for safeguarding business secrets. Article 170. (1) (Amended, SG No. 17/2009, SG No. 105/2011, effective 29.12.2011) The obligation of cost orientation for specified types of access and/or interconnection shall include determination of prices on the basis of costs upon application of a cost accounting system with a view to ensuring effective and sustainable competition and maximizing consumer benefits. (2) The obligation referred to in Paragraph (1) shall be imposed where the Commission ascertains, on the basis of the analysis under Article 151 herein, a lack of effective competition on the market due to the presence of an undertaking with significant market power which might sustain prices at an excessively high level or apply a price squeeze to the detriment of end-users. (3) (Amended, SG No. 105/2011, effective 29.12.2011) Upon imposition of the obligation referred to in Paragraph (1), the Commission shall take into consideration the investments made by the undertaking providing public electronic communications networks, including in next generation networks, at a reasonable rate of return on capital employed taking into account any risks specific to a particular new investment network project. (4) (Amended, SG No. 17/2009) The obligation relating to price controls for the provision of specific types of access and/or interconnection may include applying a price cap, pricing on the basis of a comparative analysis between the prices set by the undertaking and the prices for the same services in comparable competitive markets of other Member States of the European Union, and/or determining a plan for gradual reduction of the prices for a specified period of time after which the level of prices must reach a pre-set level. Article 171. (1) (Amended, SG No. 105/2011, effective 29.12.2011) Where an obligation for cost orientation has been imposed on an undertaking providing public electronic communications networks, in applying the cost accounting system developed by the said undertaking, the burden of proof that the charges set thereby are derived from costs, including a reasonable rate of return on investment, shall lie with the undertaking concerned. (2) (Amended, SG No. 105/2011, effective 29.12.2011) For the purpose of calculating the cost of efficient provision of services, the Commission may use cost accounting methods independent of the methods used by the undertaking concerned. (3) The Commission may require the undertaking referred to in Paragraph (1) to provide full justification of the prices and, where necessary, to adjust the said prices. Article 172. (1) (Amended, SG No. 105/2011, effective 29.12.2011) An undertaking on which an obligation has been imposed to develop and implement a cost accounting system, shall make a description of the said system publicly available, showing at least the main categories under which costs are grouped and the rules used for the allocation of costs. (2) The Commission shall order a verification of compliance with the cost accounting system by an independent auditor, and the results of the said verification shall be published annually. Article 172a. (New, SG No. 105/2011, effective 29.12.2011) (1) The Commission may impose an obligation on a vertically integrated undertaking with significant market power in a relevant market to place activities related to the wholesale provision of access services in an independently operating