  We study the fused currents of the deformed Virasoro algebra (DVA). By
constructing a homotopy operator we show that for special values of the
parameter of the algebra fused currents pairwise coincide on the cohomologies
of the Felder resolution. Within the algebraic approach to lattice models these
currents are known to describe neutral excitations of the solid-on-solid (SOS)
models in the transfer-matrix picture. It allows us to prove the closeness of
the system of excitations for a special nonunitary series of restricted SOS
(RSOS) models. Though the results of the algebraic approach to lattice models
were consistent with the results of other methods, the lack of such proof had
been an essential gap in its construction.
