Stability of Critical Points under Small Perturbations. Part I: Topological Theory. Michael Reeken — 1972 Manuscripta mathematica
Stability of Critical Points under Small Perturbations. Part II: Analytic Theory. Michael Reeken — 1973 Manuscripta mathematica
Stability of Critical Values and Isolated Critical Continua. Michael Reeken — 1974 Manuscripta mathematica