  Koszul modules over Noetherian local rings $R$ were introduced by Herzog and
Iyengar and they possess good homological properties, for instance their
Poincare' series is rational. It is an interesting problem to characterize
classes of Koszul modules. Following the idea traced by Avramov, Iyengar and
Sega, we take advantage of the existence of special filtration on $R$ for
proving that large classes of $R$-modules over Koszul rings are Koszul modules.
By using this tool we reprove and extend some results obtained by Fitzgerald.
