Hambrock, Kenneth O. & Miller, George T. Boron Isotope Enrichment: Pilot Plant Proposal for the Anisole - BF₃ System, report, December 23, 1957; (https://digital.library.unt.edu/ark:/67531/metadc860822/m1/1/: accessed December 13, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; .