SOCIAL SECURITY FOR MIGRANT WORKERS - LEGISLATION APPLICABLE - LEGISLATION OF THE MEMBER STATE IN WHICH THE WORKER WAS LAST EMPLOYED - NO ACTIVITY CARRIED ON FOR A SUBSTANTIAL PERIOD - IMMATERIAL - SIMULTANEOUS APPLICATION OF MORE THAN ONE NATIONAL LEGISLATIVE SYSTEM - NOT POSSIBLE ( REGULATION ( EEC ) NO 1408/71 OF THE COUNCIL , ART . 13 ( 2 ) ( A ))