Preface.- Critical Points of Functionals.- Minimax Systems.- Examples of Minimax Systems.- Ordinary Differential Equations.- The Method using Flows.- Finding Linking Sets.- Sandwich Pairs.- Semilinear Problems.- Superlinear Problems.- Weak Linking.-Resonance Problems.- Rotationally Invariant Solutions.- Semilinear Wave Equations.-Type (II) Regions.- Weak Sandwich Pairs.- Multiple Solutions.- Second Order Periodic Systems.- Bibliography.