Frontmatter -- Preface / Lefschetz, Solomon -- Contents -- I. On the Non-Linear Difference-Differential Equation y1(t) = [A - By(t-r) ly (t) / Kakutani, S. / Markus, L. -- II. On the Critical Points of a Class of Differential Equations / Lefschetz, Solomon -- III. Optimal Discontinuous Forcing Terms / Bushaw, D. -- IV. On the Structure of Symmetric Periodic Solutions of Conservative Systems, with Applications / DeVogelaere, René -- V. Asymptotic Behavior of Solutions of Canonical Systems Near a Closed, Unstable Orbit / Slotnick, D. L. -- VI. Small Periodic Perturbations of an Autonomous System of Vector Equations / Kyner, Walter T. -- VII. Rotated Vector Fields and an Equation for Relaxation Oscillations / Seifert, George -- VIII. A Survey of Lyapunov's Second Method / Antosiewicz, H. A. -- IX. On Phase Portraits of Critical Points in n-Space / Mendelson, Pinchas -- X. On Non-Linear Repulsive Forces / Bass, Robert W. -- Backmatter |