1. European Commission Renewable Energy Directivehttps://ec.europa.eu/energy/en/topics/renewable-energy/renewable-energy-directive
2. Eurostat Share of Energy from Renewable Sourceshttps://appsso.eurostat.ec.europa.eu/nui/show.do
3. Net-zero emissions energy systems
4. Eurostat Share of Energy from Renewable Sources in Transport, 2004–2018 (% of Gross Final Energy Consumption)https://ec.europa.eu/eurostat/statistics-explained/index.php?title=File:Share_of_energy_from_renewable_sources_in_transport,_2004-2018_(%25_of_gross_final_energy_consumption).png
5. Hydrogen-Powered Aviation: A Fact-Based Study of Hydrogen Technology, Economics and Climate Impact by 2050,2020