Oliveira, David, and Isabel Mendes. “Green Taxation on Competitiveness: The Effect of the ISP Tax on the Portuguese Retail Sector of Road Fuels”. International Journal of Energy Economics and Policy 7, no. 1 (January 17, 2017): 178–184. Accessed April 15, 2024. https://www.econjournals.com/index.php/ijeep/article/view/3652.