Cathal Flynn, The regulation of number porting services in the EU : Are the principles set out by the ECJ in the recent PTC decision reconcilable with the practical consequences of the earlier Mobistar judgment? Case comment to the preliminary ruling of the Court of Justice of 1 July 2010 Polska Telefonia Cyfrowa v President of Office of Electronic Communications (Case C-99/09) , Yearbook of Antitrust and Regulatory Studies, 2011, 4 (5), , s. 241-254