@article{10_4064_am_24_3_243_250,
     author = {A. Gasull and R. Prohens},
     title = {Effective computation of the first {Lyapunov} quantities for a planar differential equation},
     journal = {Applicationes Mathematicae},
     pages = {243--250},
     publisher = {mathdoc},
     volume = {24},
     number = {3},
     year = {1997},
     doi = {10.4064/am-24-3-243-250},
     zbl = {0882.34038},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/am-24-3-243-250/}
}