“…For a given conformal invariant background, we need to solve for the spectrum of stringy excitations and calculate the scattering amplitudes separately. One can gather many useful information and interesting patterns from different backgrounds and various kinematic limits [13,14,15,16,17,18,19,20,21,22,23,24,25,26,27]. However, if we wish to look for a symmetry principle underlying string theory, we should be able to relate these symmetry patterns and extract a universal property from these calculations.…”