American Standard safety code for installing and using electrical equipment in and about coal mines (M2.1) : revision of American Standard safety rules for installing and using electrical equipment in coal mines, M2-1926 / American Standards Association ; sponsors, American Mining Congress and U.S. Bureau of Mines. (Bulletin)
American Standard safety code for installing and using electrical equipment in and about coal mines (M2.1) : revision of American Standard safety rules for installing and using electrical equipment in coal mines, M2-1926 / American Standards Association ; sponsors, American Mining Congress and U.S. Bureau of Mines.