Huttl, J.B., 1941, Making a three-metal separation at the Duquesne group: Engineering and Mining Journal, v. 142, no. 11, p. 56-58.
Huttl, J.B.
Engineering and Mining Journal, v. 142, no. 11, p. 56-58.
Mineral District, Mining Engineering, Ore, Copper, Lead, Zinc, Silver,
