@article{JRAM_1984__355_152689,
     author = {Franz Rothe},
     title = {The periods of the {Volterra-Lotka} system.},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {129--138},
     year = {1984},
     volume = {355},
     zbl = {0547.92011},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1984__355_152689/}
}