Gasper-Galvin, L.D.; Fisher, E.P. & Goyette, W.J. Manganese-based sorbents for coal gas desulfurization, report, December 31, 1996; (https://digital.library.unt.edu/ark:/67531/metadc687536/m1/1/: accessed October 22, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; .