Popp, D. (2001). Pollution control innovations and the clean air act of 1990. National Bureau of Economic Research.
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रPopp, David. Pollution Control Innovations and the Clean Air Act of 1990. Cambridge: National Bureau of Economic Research, 2001.
एमएलए (9वां संस्करण) प्रशस्ति पत्रPopp, David. Pollution Control Innovations and the Clean Air Act of 1990. National Bureau of Economic Research, 2001.
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