An article for treating a gas containing nitrogen oxides having a monolith substrate loaded with a catalytic composition containing at least one catalytic component consisting of (i) at least one transition metal dispersed on a mixed oxide or composite oxide or a mixture thereof as support material consisting of cerium and zirconium; or (ii) cerium oxide and zirconium oxide as single oxides or a composite oxide thereof or a mixture of the single oxides and the composite oxide dispersed on an inert oxide support material, wherein at least one transition metal is dispersed thereon, wherein the at least one transition metal is selected from the group consisting of a metal from Group VIB, IB, IVA, VB, VIIB, and VIII and mixtures of any two or more thereof, provided that at least one selected transition metal is tungsten, wherein the catalytic composition is disposed on said monolith substrate.