  In 2005 Lorenzoni and Magri showed that a hydrodynamic-type hierarchy
determined by the powers of a type (1,1) tensor field (on a smooth manifold)
with vanishing Nijenhuis torsion can be deformed to a more general hierarchy,
with the help of a chain of conservation laws of the new hierarchy. We review
this construction. The (1,1) tensor fields of the resulting hierarchy have
non-vanishing Nijenhuis torsion, in general, but their Haantjes tensor
vanishes.
