1. European Commission, “Air Quality Standards: Environment,” http://ec.europa.eu/environment/air/quality/standards.htm.
2. Directive 2008/50/EC of the European Parliament and of the council of 21 May 2008 on ambient air quality and cleaner air for Europe, Official J. European Union, L 152(1) (2008).
3. European Environment Agency, “Air Quality in Europe — 2017 Report,” EEA Report, 13, (2017). https://www.eea.europa.eu/publications/air-quality-in-europe-2017/.
4. European Environment Agency, “Air Quality in Europe — 2018 Report,” EEA Report, 12 (2018), https://www.eea.europa.eu//publications/air-quality-in-europe-2018.
5. Particulate air pollution and mortality in 38 of China’s largest cities: time series analysis