1. United Nations, “Adoption of the Paris agreement,” Paris, 2015, doi:FCCC/CP/2015/L.9/Rev.1.
2. Organization, W.H., “Who Air quality guidelines for particulate matter, ozone, nitrogen dioxide and sulfur dioxide,” Geneva, 2005, doi:WHO/SDE/PHE/OEH/06.02.
3. Reay, D., Sabine, C., Smith, P., and Hymus, G., “Spring-time for sinks,” Nature 446(7137):727–728, 2007, doi:10.1038/446727a.
4. European Environment Agency, “Air quality in Europe—2013 Report: EEA report no 9/2013,” ISBN 9789292134068, 2013.
5. United States Environmental Protection Agency, “Global Emissions by Gas Global Emissions,” Gas Emiss. (2014):1–6, 2017.