++++ 1 . SOCIAL SECURITY FOR MIGRANT WORKERS - RIGHTS OF PERSONS CONCERNED - REDUCTIONS - PROHIBITION - LIMITATION CONSTITUTING THE COUNTERBALANCE TO COMMUNITY ADVANTAGES - PERMISSIBILITY ( EEC TREATY, ARTICLE 48 AND ARTICLE 51 ) 2 . SOCIAL SECURITY FOR MIGRANT WORKERS - MORE THAN ONE LEGISLATIVE SYSTEM - APPLICATION - ARTICLE 12 OF REGULATION NO 3 - AIM - BENEFITS DUE UNDER ONE LEGISLATIVE SYSTEM - REDUCTION - IMPERMISSIBLE 3 . SOCIAL SECURITY FOR MIGRANT WORKERS - OLD-AGE AND DEATH INSURANCE - RIGHT ACQUIRED BY VIRTUE OF INSURANCE PERIODS COMPLETED UNDER THE LEGISLATION OF A SINGLE MEMBER STATE - REDUCTION BY WAY OF AGGREGATION AND APPORTIONMENT - PROHIBITION ( REGULATION NO 3 OF THE COUNCIL, ARTICLE 27 AND ARTICLE 28 ) 4 . SOCIAL SECURITY FOR MIGRANT WORKERS - OLD-AGE AND DEATH INSURANCE - INSURANCE PERIODS COMPLETED UNDER THE LEGISLATION OF SEVERAL MEMBER STATES - OVERLAPPING - CONCEPT ( REGULATION NO 3 OF THE COUNCIL, ARTICLE 27 )