Productivity of underground coal workings.
Series: United Nations. Document; ST/ECE/Coal/13; [Document] (United Nations) ;; ST/ECE/Coal/13.
Publisher: United Nations
Published: 1965
Place of publication: New York
Language: eng; jpn
Number of pages: 188
Subjects: Coal mines and mining.
Notes: "United Nations publications. Sales no.: 65.II.E/Mim.21."