Segments of normalized mean profiles. In the upper panel three normalized mean profiles of the G-1 bursts at the energies of 2.5 (thick black line), 7.5 (thin blue line), and 12.5 keV (red thick line) are shown. Short vertical lines mark the maxima of P1 and the long vertical line marks the shoulder. The lower panel presents segments of normalized mean profiles of the G-3III bursts in some energy channels from the lowest (3.5 keV, thick black line) to the highest one (14.4 keV, red thick line). Long vertical lines mark the maxima of P2 and the minima in valley between P1 and P2; short vertical lines mark the maxima of P1 at the extreme energies. We note the constant time distance between the minimum between P1 and P2, the maxima of P2 and P3, while the time of the P1 maximum shifts by 2.5 s.