1. Abraham, R.: Foundations of mechanics. New York-Amsterdam: Benjamin 1967
2. Guckenheimer, J.: Catastrophes and partial differential equations. To appear
3. Mather, J.: (Unpublished, handwritten notes, apparently widely distributed, often referred to as notes on right-equivalence, after the title of the first chapter) (1969)
4. Porteous, I.: The normal singularities of a submanifold. J. Diff. Geom.5, 543?564 (1971)
5. Thom, R.: Stabilité structurelle et morphogénèse. Reading, Massachusetts: Benjamin 1972