Distribution of the spectral peak energies (left) and the low-energy spectral power-law indices (right). The sample of INTEGRAL GRBs is shown in black; BATSE results (violet) and Fermi/GBM results (red) of the time-integrated spectral analysis were used for comparison. Only long events were selected, fitted with the Band or cut-off power-law model, and having a fluence in the same range as INTEGRAL GRBs.