[en] In order to apply the Doppler broadening to the resonances a method enabling the treatment of any pointwise cross sections has been built in the code ETOBOX. This method can utilize the precise thermal kernel as well as a simplified kernel. It is shown that the functions psi and chi applied to resonances described by the Breit-Wigner model are derived from the simplified kernel. Finally, comparison between the two kernels in the case of U-238 shows that the simplified kernel can be used in all practical cases. (author)