Long GRBs, time-resolved analysis: distribution of the spectral indices, according to the best fit model, for the time-resolved fits of the eight long GRBs showing a spectral break. The spectral indices α₁, α₂, and β of the 2SBPL model are shown with red, blue, and green filled histograms, respectively. Gaussian functions showing the central value and standard deviation of the distributions are overlapped to the histograms (colour-coded dashed curves). The black empty histograms represent the distributions of the two photon indices α and β of the SBPL model, for spectra where the SBPL is the best fit model.