  We consider in this paper a large class of perturbed semilinear wave
equations with critical (in the conformal transform sense) power nonlinearity.
We will show that the blow-up rate of any singular solution is given by the
solution of the non-perturbed associated ODE. The result in the radial case has
been proved in [13]. The same approach will be followed here, but the main
difference is to construct a Lyapunov functional in similarity variables valid
in the non-radial case, which is far from being trivial. That functional is
obtained by combining some classical estimates and a new identity of the
Pohozaev type.

Analysis of PDEs