. . "Coal Specifications United States." . . "Geological Survey (U.S.)," . . "Geological Survey (U.S.)" . "Coal Purchasing United States." . . . . . "The purchase of coal under government and commercial specifications on the basis of its heating value : with analyses of coal delivered under government contracts"@en . "Specifications"@en . . "The purchase of coal under government and commercial specifications on the basis of its heating value, with analyses of coal delivered under government contracts"@en . "The purchase of coal under government and commercial specifications on the basis of its heating value : with analyses of coal delivered under government contracts" . . . . . . . . . . "The Purchase of coal under government and commercial specifications on the basis of its heating value" . . . . . . . . . . . "The Purchase of coal under government and commercial specifications on the basis of its heating value, with analyses of coal delivered under government contracts, by D. T. Randall" . "Coal United States Analysis." . .