Multiple Solutions for $4$-superlinear Klein-Gordon-Maxwell System Without Odd Nonlinearity

Infinitely many solutions via critical points for a fractional p-Laplacian equation with perturbations

“…to ensure that the energy functional satisfies the Palais-Smale condition, i.e., (PS) sequence has a convergent subsequence; this condition can also be found in [26,28,[40][41][42]. There are only a few papers on (1) with a sublinear perturbation.…”