We take advantage of the complex structure to compute in a short way and without using any computer algebra system the Lyapunov quantities and for a general smooth planar system.
@article{bwmeta1.element.bwnjournal-article-zmv24i3p243bwm, author = {A. Gasull and R. Prohens}, title = {Effective computation of the first Lyapunov quantities for a planar differential equation}, journal = {Applicationes Mathematicae}, volume = {24}, year = {1997}, pages = {243-250}, zbl = {0882.34038}, language = {en}, url = {http://dml.mathdoc.fr/item/bwmeta1.element.bwnjournal-article-zmv24i3p243bwm} }
Gasull, A.; Prohens, R. Effective computation of the first Lyapunov quantities for a planar differential equation. Applicationes Mathematicae, Tome 24 (1997) pp. 243-250. http://gdmltest.u-ga.fr/item/bwmeta1.element.bwnjournal-article-zmv24i3p243bwm/
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