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| | Explanatory Text for the Geologic Map of the U.S. - Part 4 |
 | | Hack, J. T., 1955, Geology of the Brandywine area and origin of the upland of southern Maryland, in Geology and soils of the Brandywine area, Maryland: U.S. Geol. |
 | | Hitchcock, C. H., and Blake, W. P., 1874, Geological map of the United States, compiled from sources mentioned in the text, in Walker, F. W., ed., Statistical Atlas of the United States, based on the results of the Ninth Census, 1870, compiled under the authority of Congress: Washington, pl. 12-14, and p. |
 | | Hitchcock, Edward, 1854, Outlines of the geology of the globe, and of the United States in particular, with two geological maps, and sketches of characteristic American fossils: Boston, 136 p., maps. |
| pubs.usgs.gov /dds/dds11/pp901_html/4_PP901.HTML (1697 words) |
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