1. AP-42, Compilation of Air Pollutant Emission Factors (EPA - U.S. Environmental Protection Agency); https://www.epa.gov/air-emissions-factors-and-quantification/ap-42-compilation-air-emissions-factors.
2. EMEP/EEA air pollutant emission inventory guidebook (EEA - European Environmental Agency); https://www.eea.europa.eu/publications/emep-eea-guidebook-2016.
3. Updated unified methodology for inventory of harmful substance emissions in the air, approved by the Bulgarian Ministry of Environment and Water; http://www.eea.government.bg/.
4. Annual environmental reports, http://eea.government.bg/bg/r-r/r-kpkz/godishni-dokladi-14/index.
5. Reports from own measurements conducted by „IKOMET” Ltd. provided by the legal entity.