1. N. K. Gavrilov and L. P. Shil'nikov, ?Three-dimensional dynamical systems similar to a system with nonstructurally stable homocinic curve. I,? Mat. Sb.,88, No. 4, 475?492 (1972); II,90, No. 1, 139?157 (1973).
2. J. Palis, ?A differentiable invariant of topological conjugacies and moduli of stability,? Asterisque, No. 51, 335?346 (1978).
3. S. V. Gonchenko and L. P. Shil'nikov, ?Dynamical systems with nonstructurally stable homoclinic curves,? Dokl. Akad. Nauk SSSR,286, No. 5, 1049?1053 (1986).
4. S. V. Gonchenko, ?Nontrivial hyperbolic subsets of systems with a nonstructurally stable homoclinic curve,? in: Methods of Qualitative Theory of Differential Equations [in Russian], Gorkii State Univ. (1984), pp. 89?102.
5. S. Newhouse, J. Palis, and F. Takens, ?Bifurcations and stability of families of diffeomorphisms,? Math. IHES, No. 57, 5?72 (1983).