Recursion operators for a class of integrable third-order evolution equations

We consider u(t) = u(alpha)u(xxx) + n(u)u(x)u(xx) + m(u)u(x)(3) + r(u)u(xx) + p(u)u(x)(2) + q(u)u(x) + s(u) with alpha = 0 and alpha = 3, for those functional forms of m, n, p, q, r, s for which the equation is integrable in the sense of an infinite number of Lie-Backlund symmetries. Recursion operators which are x- and t-independent that generate these infinite sets of (local) symmetries are obtained for the equations. A combination of potential forms, hodograph transformations, and x- generalized hodograph transformations are applied to the obtained equations.