... 0 in H and a constant α such that J/∂D ≤ α,b there is a constant β>αsuch that J/H ≥ β,c J satisfies the Palais-Smale condition (PS).Then, the functional J has a critical point in ... Differential Equations,CBMSRegional Conference Series in Mathematics, no. 65, American Mathematical Society, Providence, RI,USA, 1986.10 P. H. Rabinowitz, “Some minimax theorems and applications ... oscillations,”Journal of Mathematical Analysis and Applications, vol. 21, pp. 421–425, 1968.6 Boundary Value ProblemsLet wk be an arbitrary sequence bounded in H. It follows from 3.12 and the Schwarzinequality...