"February 1979. Base 4-R-36952." "Base compiled from USGS quadrangle sheets and Texas general highway map." "20,000 foot grid ticks based on Texas state plane coordinate system, north central zone." Includes location map. Available also through the Library of Congress Web site as a raster image.
United States. Soil Conservation Service
<a rel="nofollow" class="external free" href="https://www.loc.gov/item/86694271/">https://www.loc.gov/item/86694271/</a>