1. ClientEarth (2019) What are environmental principles? Retrieved June 2019 from https://www.clientearth.org/latest/latest-updates/stories/what-are-environmental-principles/
2. EPA (2016) EPA and a brief history of environmental law in the United States. Retrieved June 2021 from https://cfpub.epa.gov/si/si_public_record_report.cfm?Lab=NERL&dirEntryId=319430
3. EPA (2017) Clean air act requirements and history. Retrieved June 2021 from https://www.epa.gov/clean-air-act-overview/clean-air-act-requirements-and-history
4. EPA (2020a) History of the Clean Water Act. Retrieved June 2021 from https://www.epa.gov/laws-regulations/history-clean-water-act
5. EPA (2020b) What is the National Environmental Policy Act? Retrieved June 2021 from https://www.epa.gov/nepa/what-national-environmental-policy-act