1. Communication from the Commission to the European Parliament and the Council: an action plan to strengthen the fight against tax fraud and tax evasion (2016). https://eur-lex.europa.eu/legal-content/en/TXT/?uri=CELEX%3A52012DC0722
2. Vavouras, I., Kourtis, A.: Informal Economy: The Extent of the Phenomenon in Greece and Abroad. Papazisis eds, Athens (1991)
3. Kazantzis, C.: Auditing and Internal Control: A Systematic Approach to Concepts, Principles and Standards. Business Plus S.A, Piraeus (2006)
4. Karagiorgos, T.: Tax Practice. Germanos eds, Thessaloniki (2003)
5. Koromilas, G.L.: Income Tax Code, Law 4172/2013 (Journal of Laws 167/A) Analysis and Interpretation, Athens (2013)