“…Both hierarchies can be found in [23] and references therein. They have been studied through the constraint flows [11,23], source-generating approach [3,20] and introducing a new time variable in the frame of Sato' theory [12,15]. Several methods are used to solve those equations including the inverse scattering transform (IST) [1,2,11,23], Daboux transform [13,14,21,24], bilinear method [3,20,25,26], etc.…”