Mattoon, Wilbur R. (Wilbur Reed), 1875-1941. & Reed, C. A. (Clarence Arthur), 1880-1950. Black walnut for timber and nuts., book, 1940; (https://digital.library.unt.edu/ark:/67531/metadc9514/m1/1/: accessed October 16, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; .