Não informado. (2021). Annual Bulletin of Coal Statistics for Europe and North America. United Nations.
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रNão informado. Annual Bulletin of Coal Statistics for Europe and North America. New York: United Nations, 2021.
एमएलए (8वां संस्करण) प्रशस्ति पत्रNão informado. Annual Bulletin of Coal Statistics for Europe and North America. United Nations, 2021.
चेतावनी: ये उद्धरण हमेशा 100% सटीक नहीं हो सकते हैं.