1 . SOCIAL SECURITY FOR MIGRANT WORKERS - VOLUNTARY INSURANCE - SPECIAL WAYS OF GIVING EFFECT TO CERTAIN LAWS - FEDERAL REPUBLIC OF GERMANY - PARAGRAPHS 8 AND 9 OF PART C OF ANNEX V TO REGULATION NO 1408/71 - CONDITION OF RETROGRESSIVE BUYING-IN LAID DOWN BY NATIONAL LEGISLATION - SCOPE - GERMAN NATIONAL WHO HAS PAID CONTRIBUTIONS TO OLD-AGE PENSION INSURANCE IN ANOTHER MEMBER STATE ( PARAGRAPHS 8 AND 9 OF PART C OF ANNEX V TO REGULATION NO 1408/71 OF THE COUNCIL , AS AMENDED BY REGULATION NO 1392/74 ) 2 . SOCIAL SECURITY FOR MIGRANT WORKERS - VOLUNTARY INSURANCE - SPECIAL WAYS OF GIVING EFFECT TO CERTAIN LAWS - FEDERAL REPUBLIC OF GERMANY - PARAGRAPHS 8 AND 9 OF PART C OF ANNEX V TO REGULATION NO 1408/71 - CONDITION OF RETROGRESSIVE BUYING-IN LAID DOWN BY NATIONAL LEGISLATION - DISCRIMINATION AGAINST GERMAN WORKERS AND FOREIGNERS RESIDING IN THE FEDERAL REPUBLIC OF GERMANY - NONE ( PARAGRAPHS 8 AND 9 OF PART C OF ANNEX V TO REGULATION NO 1408/71 OF THE COUNCIL , AS AMENDED BY REGULATION NO 1392/74 ) 3 . COMMUNITY LAW - PRINCIPLES - EQUAL TREATMENT - CONCEPT