5Axel H BOrsch-Supan, Christina B Wilke. The german public pension system. How it was, how it will be[R]. MEA Discussion Paper,2003.13-15.
6CBO(Congress of the United States, Congressional Budget Office). The 2005 annual report of the board of trustees of the federal old-age and survivors insurance and disability insurance trust funds[R]. 109th Congress: 1st Session House Document, 2005:23-38.
