On bi-hamiltonian geometry of some integrable systems on the sphere with   cubic integral of motion
  We obtain bi-Hamiltonian structure for a family of integrable systems on the sphere S with an additional integral of third order in momenta. These results are applied to the Goryachev system and Goryachev-Chaplygin top for which we give an explicit procedure to find the separated coordinates and the separated relations. 
A V Vershilov and A V Tsiganov