1. T.S. Eliot, The Hollow Men (1925); see Complete Poems and Plays (1909–1950), Harcourt, Brace & World, Inc. New York (1934), p. 56.
2. J. Burckhardt, Reflections on History, Liberty Classics, Indianapolis (1979), p. 319
3. P. Hohnes, this volume (1989)
4. J. Guckenheimer, P. Holmes,Nonlinear Oscillations, Dynamical Systems and Bifurcation of Vector Fields, Springer (1983)
5. N. Aubry, P. Holmes, J.L. Lumley, E. Stone, J. Fluid Mech. 192, 115 (1988)