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The impact of tax morale and institutional quality on the shadow economy
Schneider, Friedrich, (2007)
Shadow economy, tax morale, governance and institutional quality: A panel analysis
Towards a common migration policy: potential impact on the EU economy
Biffl, Gudrun, (2006)
Informal and underground economy
Frey, Bruno S., (2000)
What are the sources of happiness?
Direct Democracy for a Living Constitution
Frey, Bruno S., (2004)