  An analysis of previous theories of superfluidity of quantum solids is
presented in relation to the nonclassical rotational moment of inertia (NCRM)
found first in Kim and Chan experiments. A theory of supersolidity is proposed
based on the presence of an additional conservation law. It is shown that the
additional entropy or mass fluxes depend on the quasiparticle dispersion
relation and vanish in the effective mass approximation. This implies that at
low temperatures when the parabolic part of the dispersion relation
predominates the supersolid properties should be less expressed.
