Wang, C.T.; Barock, E.F.; La Vake, J.C. & Christopher, S.S. VANADIUM PURIFICATION. Sixth Quarterly Progress Report, January 1--March 31, 1968., report, January 1, 1968; (https://digital.library.unt.edu/ark:/67531/metadc1034825/m1/1/: accessed October 22, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; .