1. Arjomandi, A., Gholipour, H. F., Tajaddini, R. and Harvie, C. (2022). Environmental expenditure, policy stringency and green economic growth: evidence from OECD countries. Applied Economics, Vol. 55, No. 8, pp. 869-884.
2. Breitung, J. (2000). The Local Power of Some Unit Root Tests for Panel Data. In B. Baltagi (ed.), Advances in Econometrics, Vol. 15: Nonstationary Panels, Panel Cointegration, and Dynamic Panels, Elsevier Science Inc.
3. Boyd, J. (2009) Green GDP: 'Seeing' the Hidden Economy of Nature. Resources for the Future, a part of Research Paper 09-35 with Alan Krupnick. Washington, DC. Available at: http://www.cirano.qc.ca/icirano/public/pdf/GDPMontreal2.pdf.
4. European Environment Agency (2023). Environmental protection expenditure; Analysis and data. Available at:https://www.eea.europa.eu/en/analysis/indicators/environmental-protection-expenditure-8th-eap.
5. Eurostat (2024). Eurostat database. Available at: https://ec.europa.eu/eurostat.