References
- Lando , C. 1971 . J. Diff. Eq.s . 9 : 262 – 279 .
- Gomory , R. 1956 . Ann. Math. Studies . 36 : 85 – 126 .
- Cronin , J. 1960 . Duke Math. J . 27 : 183 – 94 .
- 1965 . J. Diff. Ea.s . 1 : 156 – 94 .
- Lefschetz , S. 1963 . Differential Equations: Geometric Theory , 209 – 214 . Chapt : Wiley-Interscience .