@article{AIHPA_1993__59_1_99_0,
     author = {Castilla, M. S. A. C. and Moauro, Vinicio and Negrini, Piero and Oliva, Waldyr Muniz},
     title = {The four positive vortices problem : regions of chaotic behavior and the non-integrability},
     journal = {Annales de l'I.H.P. Physique th\'eorique},
     pages = {99--115},
     publisher = {Gauthier-Villars},
     volume = {59},
     number = {1},
     year = {1993},
     mrnumber = {1244184},
     zbl = {0792.76010},
     language = {en},
     url = {http://www.numdam.org/item/AIHPA_1993__59_1_99_0/}
}