By means of a variational identity of Poho\v{z}aev-Pucci-Serrin type for
solutions of class C1 recently obtained, we give some necessary conditions
for locating the concentration points for a class of quasi-linear elliptic
problems in divergence form. More precisely we show that the points where the
concentration occurs must be critical, either in a generalized or in the
classical sense, for a suitable ground state function.Comment: Final revised version, accepted for publicatio