Balachandran, U.; Guan, J. & Dorris, S.E. Development of proton-conducting membranes for hydrogen separation, article, July 1, 1998; (https://digital.library.unt.edu/ark:/67531/metadc703802/m1/1/: accessed November 20, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; .