++++ 1 . FREE MOVEMENT OF PERSONS - WORKERS - RELATED PROVISIONS - CRITERIA FOR INTERPRETATION ( EEC TREATY, ARTICLES 48 TO 51 ) 2 . FREE MOVEMENT OF PERSONS - WORKERS - MANDATORY APPLICATION OF THE LEGISLATION OF THE STATE IN WHICH THE PERSON CONCERNED IS EMPLOYED ( EEC TREATY, ARTICLES 48 TO 51; REGULATION N . 3 OF THE COUNCIL OF THE EEC OF 25 SEPTEMBER 1958 CONCERNING SOCIAL SECURITY FOR MIGRANT WORKERS ( OFFICIAL JOURNAL OF 16 DECEMBER 1958 ), ARTICLE 12 ) 3 . FREE MOVEMENT OF PERSONS - WORKERS - SIMULTANEOUS APPLICATION OF SEVERAL SYSTEMS OF LEGISLATION - ADMISSIBILITY OF PRINCIPLE - PERMISSIBILITY OF GRANT OF SUPPLEMENTARY PROTECTION BY WAY OF SOCIAL SECURITY BY A STATE OTHER THAN THAT IN WHICH THE PERSON CONCERNED IS EMPLOYED