Two-component generalizations of the Camassa-Holm equation
  A classification of integrable two-component systems of non-evolutionary partial differential equations that are analogous to the Camassa-Holm equation is carried out via the perturbative symmetry approach. Independently, a classification of compatible pairs of Hamiltonian operators is carried out, which leads to bi-Hamiltonian structures for the same systems of equations. Some exact solutions and Lax pairs are also constructed for the systems considered. 
Andrew N.W. Hone, Vladimir Novikov and Jing Ping Wang
nlin.SI