1. Mishchenko, E.F., Kolesov, Yu.S., Kolesov, A.Yu., and Rozov, N.Kh., Periodicheskie dvizheniya i bifurkatsionnye protsessy v singulyarno-vozmushchennykh sistemakh (Periodic Motions and Bifurcation Processes in Singularly Perturbed Systems), Moscow, 1995.
2. Bobkova, A.S., Kolesov, A.Yu., and Rozov, N.Kh., Mat. Zametki, 2002, vol. 71, no.6, pp. 818?831.
3. Bobkova, A.S., Differents. Uravn., 2004, vol. 40, no.10, pp. 1305?1313.
4. Kolesov, A.Yu., Mishchenko, E.F., and Rozov, N.Kh., Trudy Mat. Inst. im. V.A. Steklova RAN, 1999, vol. 224, pp. 187?207.
5. Lebovitz, N.R. and Schaar, R.J., Stud. Appl. Math., 1975, vol. 54, pp. 229?260.