Roger, Chris; Mountz, David; He, Wensheng & Zhang, Tao. Durable, Low-cost, Improved Fuel Cell Membranes, report, March 17, 2011; (https://digital.library.unt.edu/ark:/67531/metadc833775/m1/1/: accessed November 17, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; .