Upper bound for the number of critical levels for nonlinear operators in Banach spaces of the type of second order nonlinear partial differential operators

This publication has 3 references indexed in Scilit:

• LJUSTERNIK‐SCHNIRELMANN Theorem and Nonlinear Eigenvalue Problems
  Mathematische Nachrichten, 1972
• Infinite Dimensional Manifolds and Non-Linear Elliptic Eigenvalue Problems
  Annals of Mathematics, 1965
• Estimates near the boundary for solutions of elliptic partial differential equations satisfying general boundary conditions. I
  Communications on Pure and Applied Mathematics, 1959