Bulgakov, Andrey, and Arseniy Krikunov. “The Harmonization of Eco-Efficiency Standards: An Analysis on the Energy Enterprises of the G7 Group and the Emerging E7 Countries”. International Journal of Energy Economics and Policy, vol. 10, no. 2, Jan. 2020, pp. 227-32, https://econjournals.com./index.php/ijeep/article/view/9065.