Projective-geometric aspects of homogeneous third-order Hamiltonian   operators
  We investigate homogeneous third-order Hamiltonian operators of differential-geometric type. Based on the correspondence with quadratic line complexes, a complete list of such operators for two and three components is obtained. 
Eugene V. Ferapontov, Maxim V. Pavlov, Raffaele F. Vitolo
nlin.SI