++++ 1.Preliminary questions - Reference to the Court - National court or tribunal within the meaning of Article 177 of the Treaty - Definition ( EEC Treaty, Art . 177 ) 2.Social policy - Male and female workers - Equal pay - Lack of transparency in undertaking' s system of pay - Average pay for women less than that for men - Burden of proof of non-discrimination - Application of criteria for pay supplement - Conditions ( EEC Treaty, Art . 119; Council Directive 75/117, Arts 1 and 6 )