Coupled Integrable Systems Associated with a Polynomial Spectral Problem   and their Virasoro Symmetry Algebras
  An isospectral hierarchy of commutative integrable systems associated with a polynomial spectral problem is proposed. The resulting hierarchy possesses a recursion structure controlled by a hereditary operator. The nonisospectral flows generate the time first order dependent symmetries of the isospectral hierarchy, which constitute Virasoro symmetry algebras together with commutative symmetries. 
Wen-Xiu MA (Paderborn Univ.) and Zi-Xiang ZHOU (Fudan Univ.)