Darboux Transformations Associated with Boiti-Tu Eigenvalue Problem

To the hierarchy of nonlinear evolution equations which associate with Boiti-Tu eigenvalue problem, an explicit and universal form of Baeklund transformations and auniversal proof are presented. It is called Darboux transformation. By this method, to ask for a new solution of every system of equations of the hierarchy, it is sufficient to solve some linear problems. Here the constraints at the boundary for the potentials (for example, at x=\pm \infinity) are removed.