++++ 1. Preliminary rulings ° Reference to the Court ° Need for both parties to have been heard ° Assessment by the national court (EEC Treaty, Art. 177) 2. Preliminary rulings ° Reference to the Court ° Compliance of the decision to make a reference with the rules of national law governing the organization of the courts and their procedure ° Not a matter for the Court to verify (EEC Treaty, Art. 177) 3. Tax provisions ° Harmonization of laws ° Turnover taxes ° Common system of value added tax ° Payment of the tax after it has become chargeable ° National system requiring taxable persons to make interim payments in the nature of advances ° Incompatibility with the Sixth Directive ° Possibility for individuals to rely on the corresponding provisions (Council Directive 77/388, Arts 10 and 22(4) and (5))