1 . SOCIAL SECURITY FOR MIGRANT WORKERS - ADMINISTRATIVE COMMISSION - AUTHORIZATION BY THE COUNCIL TO ENACT MEASURES HAVING THE FORCE OF LAW - INCOMPATIBILITY WITH THE EEC TREATY - DECISIONS OF THE ADMINISTRATIVE COMMISSION - NOT BINDING ON NATIONAL AUTHORITIES ( EEC TREATY , ARTS . 155 , 173 AND 177 ; REGULATION NO 1408/71 OF THE COUNCIL , ART . 81 ) 2 . SOCIAL SECURITY FOR MIGRANT WORKERS - BENEFITS - NATIONAL RULES AGAINST OVERLAPPING - PENSION DUE UNDER THE LEGISLATION OF A SINGLE MEMBER STATE - REDUCTION ON ACCOUNT OF A PENSION GRANTED BY ANOTHER MEMBER STATE - RECOVERY OF PROVISIONAL ADVANCES - EXCHANGE RATE APPLICABLE FOR THE PURPOSE OF CALCULATING THE AMOUNT TO BE RECOVERED ( EEC TREATY , ART . 51 )