Classes of linearizable wave equations

In some recent papers we took in consideration a class of nonlinear wave equations. In those papers, we obtained its equivalence algebra $L_E$, first order differential invariant and invariant equations with respect to the equivalence group $G_E$. Further, by means of the invariant equations and/or the differential invariants, we found subclasses of linearizable equations. Here, we continue this research and characterize a new subclass of equations which can be mapped by an equivalence transformation of $G_E$ in a linear equation of the same family.