‘vertically integrated undertaking’ means an electricity undertaking or a group of electricity undertakings where the same person or the same persons are entitled, directly or indirectly, to exercise control, and where the undertaking or group of undertakings perform at least one of the functions of transmission or distribution, and at least one of the functions of generation or supply of electricity;
Source
Directive 2009/72/EC
Date 14.12.2011.