“…The isotropic variable exponent version of the Lions concentration‐compactness principle for a bounded domain was independently obtained by Bonder and Silva [
30] and Fu [
31]. Following that, many authors have applied these results to critical elliptic problems involving variable exponents (see, e.g., Alves and Ferreira [
26], Alves and Barreiro [
32], Chems Eddine et al [
33–35], Fu and Zhang [
36], Ho and Sim [
37], and Hurtado et al [
38], and the references therein). Moreover, when
are constant functions for all
, El Hamidi and Rakotoson [
39] have extended a concentration‐compactness principle to the anisotropic Sobolev space with constant exponents.…”