APA-viite (7. p.)
DEPARTMENT OF HEALTH AND SOCIAL SECURITY. (1987). NATIONAL INSURANCE VOLUNTARY CONTRIBUTIONS. DEPARTMENT OF HEALTH AND SOCIAL SECURITY.
Chicago-viite (17. p.)
DEPARTMENT OF HEALTH AND SOCIAL SECURITY. NATIONAL INSURANCE VOLUNTARY CONTRIBUTIONS. Londres: DEPARTMENT OF HEALTH AND SOCIAL SECURITY, 1987.
MLA-viite (9. p.)
DEPARTMENT OF HEALTH AND SOCIAL SECURITY. NATIONAL INSURANCE VOLUNTARY CONTRIBUTIONS. DEPARTMENT OF HEALTH AND SOCIAL SECURITY, 1987.
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