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Mihaylova-Goleminova, S., Malherbe, J.: Challenges Facing Member States and Candidate Countries of the European Union in the Field of Taxation, Sofia: Ciela Publishing, 2018.
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Official Documents:
Commission Communication “Taxation – more efficient EU law-making procedures” Available at: https://ec.europa.eu/info/law/better-regulation/initiatives/ares-2018-6590013_en 
Communication from the Commission “Towards a more efficient and democratic decision making in EU tax policy” Available at: https://eur-lex.europa.eu/legal-content/BG/TXT/HTML/?uri=CELEX:52019DC0008&from=EN 
Communication from the Commission, Commission Work Programme 2019 “Delivering what we promised and preparing for the future” Available at: https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX%3A52018DC0800