Rational solutions of a differential-difference KdV equation, the Toda equation and the discrete KdV equation

In this paper, a series of rational solutions are presented for a differential-difference analogue of the KdV equation, the Toda equation and the discrete KdV equation. These rational solutions are obtained using Hirota's bilinear formalism and Backlund transformations. The crucial step is the use of nonlinear superposition formulae.