As is well known,many important non

As is well known,many important nonlinear integrable equations have bilinear forms,such as KdV, Boussinesq, KP and so on. In many cases, it would be much easier todeal with a bilinear equation compared with original nonlinear form. For examplewe can find explicit exact solutions for bilinear equations by using Hirota’s directmethod. To find corresponding bilinear forms plays an important role for the successof Hirota’s method. It’s very important in the study of soliton theory to considerwhether a nonlinear equation can be transformed into bilinear form and deducemore new integrable bilinear equations.