Columbia subject headings:
Harvard subject headings:
Petroleum industry and trade--Deregulation--Oklahoma.
Petroleum industry and trade--Deregulation--United States.
Petroleum industry and trade--Environmental aspects--Oklahoma.
Petroleum industry and trade--Environmental aspects--United States
Petroleum industry and trade--Government policy--Oklahoma.
Petroleum industry and trade--Government policy--United States
Princeton subject headings:
Petroleum industry and trade--Deregulation--United States.
Petroleum industry and trade--Environmental aspects--United States.
Petroleum industry and trade--Government policy--United States.
Petroleum industry and trade--Oklahoma.