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Vanguards of the frontier : a social history of the Northern Plains and Rocky Mountains from the fur traders to the sod busters
Dick, Everett Newfon, (1941)
The marginal costs of alternative levels of water quality in the upper Mississippi River
Lewis, Robert Clark, (1970)
Zinc-Lead-Copper Resources and General Geology of the Upper Mississippi Valley District
Heyl, Allen V., (1955)