TECHNOLOGY FOCUS - POLYMERS - Preferred Resin: The cross-linkable aromatic resin containing proton-acid group is aromatic polyether cross-linkable using light, heat or electron beam. The polyether has carbonyl group, 1-10C alkenyl group or methylene group directly coupled to 1-10C alkyl group bonded to the aromatic ring. The cross-linkable aromatic resin contains 10-100 mol% of ether repeating unit of formula (1) and 0-90 mol% of ether repeating unit of formula (2).R1-R10 = H, 1-10C alkyl or alkenyl group;A1-A3 = -CH2-, -C(CH3)2-, -C(CF3)2-, -O-, -SO2- or -CO-;i-l = 0 or 1X1-X10 = H or proton-acid group of formula: -CnH2n-SO3Y, preferably proton-acid group;n = 0-10;andY = H, sodium or potassium.The hydrogen atom of the aromatic ring is optionally substituted by 1-10C alkyl or alkenyl group, proton acid group, chlorine, fluorine or trifluoro methane.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Compound: The proton conductive inorganic compound is hetero polyacid. EXAMPLE - 5,5'-carbonyl bis(2-fluoro benzene sodium sulfonate) (in g) (11.82), 4,4'-difluoro benzophenone (11.35), bis(3,5-dimethyl-4-hydroxy phenyl)methane (20.51) and potassium carbonate (13.82) were charged in a reactor. Dimethyl sulfoxide (200 ml) and toluene (160 ml) were added to the reactor and the contents were stirred in nitrogen atmosphere. The stirred mixture was heated at 135degreesC for 8 hours and water and toluene were removed. The mixture was reacted at 160degreesC for 6 hours and viscous polymer solution was obtained. The polymer solution was filtered, and dried to obtain sodium sulfonate group-containing polyether ketone powder (34.28) with yield of 85% and reduced viscosity of 1.20 dl/g. Tungstophosphoric acid 29 hydrate (1.005) dissolved in dimethyl acetamide (8.83) and sodium sulfonate group-containing polyether ketone powder (2.344) were mixed. The obtained mixed solution was applied on a glass plate and heated in nitrogen atmosphere. The formed film was cross-linked and proton exchange of the film was performed. The obtained proton-conductive film had favorable flexibility, ionic conductivity and strength.