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You searched for: Author United States. Environmental Protection Agency Remove constraint Author: United States. Environmental Protection Agency Subject Biology and Ecology Remove constraint Subject: Biology and Ecology Place Arkansas Remove constraint Place: Arkansas Place Texas Remove constraint Place: Texas
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1. Omernik's Level III Ecoregions of the Continental United States, 2003

2003. United States. Environmental Protection Agency. This polygon shapefile shows Omernik's Level III ecoregions, derived from a 1:7,500,000 map created by J.M. Omernik in 1987 and from refinements of... National Atlas of the United States.