Cita APA (7th ed.)

Popp, D. (2001). Pollution control innovations and the clean air act of 1990. National Bureau of Economic Research.

Cita Chicago (17th ed.)

Popp, David. Pollution Control Innovations and the Clean Air Act of 1990. Cambridge: National Bureau of Economic Research, 2001.

Cita MLA (9th ed.)

Popp, David. Pollution Control Innovations and the Clean Air Act of 1990. National Bureau of Economic Research, 2001.