In applications coupled oscillators are only to first order harmonic, and the aim is to understand what happens under perturbation by the nonlinear (higher order) terms. The same reason that makes the unperturbed motion particularly easy renders the perturbation analysis much more complicated when there are resonances among the (unperturbed) frequencies.
The abstract is available from the publisher and there is a review in the Zentralblatt der Mathematik 952.70017. Another review appeared in Mathematical Reviews 2000h:37093. A preprint version can be downloaded as PostScript file (3.8 M) or in a gzipped version (385 K).
The abstract is available from the publisher and appeared slightly changed in the Zentralblatt der Mathematik 999.70012. Furthermore there is a review in Mathematical Reviews 2002k:37100. A preprint version can be downloaded as PostScript file (583 K) or in a gzipped version (132 K).
The abstract is available from the publisher and appeared slightly changed in the Zentralblatt der Mathematik 1037.34031. Furthermore there is a review in Mathematical Reviews 2003f:34076. A preprint version can be downloaded as PostScript file (1.9 M) or in a gzipped version (390 K).
The abstract is available from the publisher and there are reviews in the Zentralblatt der Mathematik 1035.37038 and in Mathematical Reviews 2003d:37079. A preprint version can be downloaded as PostScript file (359 K) or in a gzipped version (128 K).
The abstract is available from the publisher and is reprinted in the Zentralblatt der Mathematik 1078.37041. Furthermore there is a review in Mathematical Reviews 2006e:37103. A preprint version can be downloaded as PostScript file (405 K) or in a gzipped version (181 K).
The abstract is available from the publisher and is reprinted in Mathematical Reviews 2009i:37138. A preprint version can be downloaded as PostScript file (5.8 M) or in pdf (684 K).
The abstract is available from the publisher and is reprinted in the Zentralblatt der Mathematik 1156.3731. Furthermore there is a review in Mathematical Reviews 2011a:37111. A preprint version can be downloaded as PostScript file (452 K) or in pdf (223 K).
The abstract is available from the publisher and there are reviews in the Zentralblatt der Mathematik 1196.37101 and in Mathematical Reviews 2011j:37118. A preprint version can be downloaded as PostScript file (489 K) or in pdf (221 K).
The abstract is available from the publisher and is reprinted in the Zentralblatt der Mathematik Zbl 06070474. Furthermore there is a review in Mathematical Reviews MR2948618. A preprint version can be downloaded as PostScript file (5.4 M) or in pdf (3.6 M).
The abstract is available from the publisher and is reprinted in the Zentralblatt der Mathematik Zbl 06137098. Furthermore there is a review in Mathematical Reviews MR2949643. A preprint version can be downloaded as PostScript file (578 K) or in pdf (357 K).