“…The cross-correlation functions between the symmetrical peaks, even if the width is different, have no time lag [see (1,2) and (2, 1)]. If the shapes of the peaks are different and if at least one of them is deformed, the crosscorrelation functions have the maxima when τ ≠ 0 [see (1,3), (1,4), (2,3), (2,4), (3,1), (3,2), (3,4), (4,1), (4,2) and (4, 3)]. …”