1. Precambrian basement map of the northern midcontinent, U.S.A. a digital representation of the 1990 P.K. Sims map / [computer file] Yale Public content 2001. 2002-06-01T04:00:00Z. 2023-02-11T04:46:16Z. Geological Survey (U.S.). The Survey ; For sale by USGS Information Services (Open-File Report Sales). English. Public. Middle West. Precambrian.