Não informado. (1974). Coal and Energy Quarterly. National Coal Board.
Chicago-Zitierstil (17. Ausg.)Não informado. Coal and Energy Quarterly. London: National Coal Board, 1974.
MLA-Zitierstil (8. Ausg.)Não informado. Coal and Energy Quarterly. National Coal Board, 1974.
Achtung: Diese Zitate sind unter Umständen nicht zu 100% korrekt.