K. Lamb, R.A. Mole, D. Yu, R. de Marco, J.R. Bartlett, S. Windsor, S.P. Jiang, J. Zhang, V.K. Peterson, Proton dynamics in phosphotungstic acid impregnated mesoporous silica proton exchange membrane materials, Green Energy & Environment (2017), doi: 10.1016/ j.gee.2017.06.007.