{. Ratto, {. Röger, {. Veld, and {. Girardi. European economy European Commission, Directorate-General for Economic and Financial Affairs, Brussels, (2005)
{. Roeger, and {. Veld. Economic papers / European Commission, Directorate-General for Economic and Financial Affairs Europ. Commission, Directorate-General for Economic and Financial Affairs, Brussels, (1997)