Não informado. Quarterly Bulletin of Coal Statistics for Europe. United Nations, Economic Commission for Europe, Coal Division.
توثيق أسلوب شيكاغو (الطبعة السابعة عشر)Não informado. Quarterly Bulletin of Coal Statistics for Europe. Geneva, Suíça: United Nations, Economic Commission for Europe, Coal Division.
توثيق جمعية اللغة المعاصرة MLA (الطبعة الثامنة)Não informado. Quarterly Bulletin of Coal Statistics for Europe. United Nations, Economic Commission for Europe, Coal Division.
تحذير: قد لا تكون هذه الاستشهادات دائما دقيقة بنسبة 100%.