IEA (2021), District heat production by region, 2020, and world average carbon intensities of district heat supply in the Net Zero Scenario, 2020-2030, IEA, Paris https://www.iea.org/data-and-statistics/charts/district-heat-production-by-region-2020-and-world-average-carbon-intensities-of-district-heat-supply-in-the-net-zero-scenario-2020-2030, Licence: CC BY 4.0