On the problem of a consistent description of kinetic and hydrodynamic   processes in dense gases and liquids: Collective excitations spectrum
  Based on the generalized non-Markovian equations obtained earlier for a nonequilibrium one-particle distribution function and potential part of the averaged enthalpy density [Markiv B.B., Omelyan I.P, Tokarchuk M.V., Condens. Matter Phys., 2010, 13, 23005] a spectrum of collective excitations is investigated, where the potential of interaction between particles is presented as a sum of the potential of hard spheres and a certain long-range potential. 
B. B. Markiv, I. P. Omelyan, M. V. Tokarchuk
cond-mat.stat-mech