SOCIAL POLICY - MEN AND WOMEN - PAY - EQUALITY - PRINCIPLE - IMPLEMENTATION BY THE MEMBER STATES - WORK TO WHICH EQUAL VALUE IS ATTRIBUTED - RIGHTS TO EQUAL PAY EVEN IN THE ABSENCE OF A SYSTEM OF JOB CLASSIFICATION - DUTIES OF THE MEMBER STATES ( EEC TREATY , ART . 119 ; COUNCIL DIRECTIVE 75/117/EEC , ART . 1 , FIRST PARAGRAPH )