Wheelwright, E.J. & Myers, T.R. PARAMETRIC EVALUATION OF DTPA, EDTA, AND HEDTA FOR ION EXCHANGE PURIFICATION OF PROMETHIUM, report, September 1, 1965; (https://digital.library.unt.edu/ark:/67531/metadc1034618/m1/1/: accessed March 21, 2019), University of North Texas Libraries, Digital Library, digital.library.unt.edu; .