Compatible Hamiltonian Operators for the Krichever-Novikov Equation

It has been proved by V. Sokolov that the Krichever-Novikov equation’s hierarchy is hamiltonian for the non-local Hamiltonian operator H_0=u_x D^{-1} u_x and possesses twi weakly non-local recursion operatos of degree 4 and 6, L_4 and L_6. We show here that H_0, L_4H_0 and L_6H_0 are compatible Hamiltonian operators for which the Krichever-Novikov equation’s hierarchy is hamiltonian.