Britton, Joseph; Britton, Michael; Britton, David & La Grove, M. Quadrula apiculata, Specimen #1011, specimen, August 23, 1979; (https://digital.library.unt.edu/ark:/67531/metadc34635/m1/1/: accessed November 19, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; .