A Proton-Conducting Polymer Membrane as Solid Electrolyte – Function and Required Properties -- Proton-Conducting Polymer Electrolyte Membranes: Water and Structure in Charge -- Structural and Morphological Features of Acid-Bearing Polymers for PEM Fuel Cells -- Perfluorinated Ionic Polymers for PEFCs (Including Supported PFSA) -- Radiation Grafted Membranes -- Advances in the Development of Inorganic–Organic Membranes for Fuel Cell Applications.