Não informado. Quarterly Bulletin of Coal Statistics for Europe. United Nations, Economic Commission for Europe, Coal Division.
শিকাগো স্টাইল (17 তম সংস্করণ) উদ্ধৃতিNão informado. Quarterly Bulletin of Coal Statistics for Europe. Geneva, Suíça: United Nations, Economic Commission for Europe, Coal Division.
M.L.A (8 ম সংস্করণ) উদ্ধৃতিNão informado. Quarterly Bulletin of Coal Statistics for Europe. United Nations, Economic Commission for Europe, Coal Division.
সতর্কবাণী: সাইটেশন সবসময় 100% নির্ভুল হতে পারে না.