Heimerl, George J. & Roy, J. Albert. Determination of desirable lengths of Z- and channel-section columns for local-instability tests, report, October 1944; (https://digital.library.unt.edu/ark:/67531/metadc62253/m1/1/: accessed April 23, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; .