  We prove the orbital stability of periodic traveling-wave solutions for
systems of dispersive equations with coupled nonlinear terms. Our method is
basically developed under two assumptions: one concerning the spectrum of the
linearized operator around the traveling wave and another one concerning the
existence of a conserved quantity with suitable properties. The method can be
applied to several systems such as the Liu-Kubota-Ko system, the modified KdV
system and a log-KdV type system.
