@article{10_1007_s10492_012_0030_y,
     author = {S\'aez, Eduardo and Sz\'ant\'o, Iv\'an},
     title = {Uniqueness of limit cycles bounded by two invariant parabolas},
     journal = {Applications of Mathematics},
     pages = {521--529},
     publisher = {mathdoc},
     volume = {57},
     number = {5},
     year = {2012},
     doi = {10.1007/s10492-012-0030-y},
     mrnumber = {2984617},
     zbl = {1262.92003},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.1007/s10492-012-0030-y/}
}