Missouri Basin studies. 11. Map showing construction materials and nonmetallic mineral resources of Montana [with text]; compiled by M. M. Knechtel, D. M. Larrabee, E. C. Fischer. A. F. Shride, R. P. Bryson. E. L. Fox. R. A. Weeks. P. S. Clabaugh, I. G. Sohn, and M. H. Krieger. Scale 1,750,000: 10 m.=0.9 in. n. p.