  Exact vacuum expectation values of the third level descendent fields
$<(\partial\phi)^3({\bar\partial}\phi)^3e^{a\phi}>$ in the Bullough-Dodd model
are proposed. By performing quantum group restrictions, we obtain $<L_{-3}{\bar
L}_{-3}{\Phi}_{lk}>$ in perturbed minimal conformal field theories.
