@article{10_4064_am_26_3_357_362,
     author = {M. Sabatini},
     title = {Quadratic {Isochronous} centers commute},
     journal = {Applicationes Mathematicae},
     pages = {357--362},
     publisher = {mathdoc},
     volume = {26},
     number = {3},
     year = {1999},
     doi = {10.4064/am-26-3-357-362},
     zbl = {1005.34022},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/am-26-3-357-362/}
}