Fizika Tverdogo Tela, 1986 Volume 28, Issue 5,Pages 1417–1424(Mi ftt295)
The anomalous behavior of soft mode decay in the incommensurate phase in $\mathrm{Cd}_{2}\mathrm{Nb}_{2}\mathrm{O}_{7}$, $\mathrm{K}_{2}\mathrm{SeO}_{4}$ and $\mathrm{Rb}_{2}\mathrm{ZnBr}_{4}$