“…By considering the importance of positon solutions, efforts have been made to identify singular positon solutions in many nonlinear integrable evolution equations including modified KdV equation [16], Toda chain [17], sine-Gordon equation [18], KdV and modified KdV hierarchies [19], fifth-order KdV equation [20], extended KdV equation [21] and KdV equation with self-consistent sources [22]. Non-singular positon solutions on vanishing background are named as smooth positons or degenerate soliton solutions [23][24][25][26][27][28][29]. This kind of solution has also been constructed for several nonlinear partial differential equations including nonlinear Schrödinger (NLS) equation [23,30], Bogoyavlensky-Konopelchenko equation [24], coupled KdV [25] and mKdV equations [26], derivative NLS equation [27], nonlocal Kundu-NLS equation [28], complex mKdV equation [29], Wadati-Konno-Ichikawa equation [31] and higher-order Chen-Lee-Liu equation [32].…”