Soliton solutions of a coupled derivative modified KdV equations

The multisoliton solution to a system of nonlinear partial differential equations which is expressed by partial derivative v(i)/partial derivative t + 6 Sigma(1 less than or equal to j<) (k less than or equal to N) C-jk (partial derivative v(j)/partial derivative(x) v(k) - v(j) partial derivative v(k)/partial derivative(x)) partial derivative v(i)/partial derivative(x) + partial derivative(3)v(i)/partial derivative x(3) = 0, for i = 1, 2, ..,N where the coefficients C-jk are arbitrary constants, is expressed by the pfaffians.