The problem of a center “in the large” for a general quadratic system
Boularas, Driss ; Vulpe, Nicolae ; Sibirskii, Constantin Sergeivitch
HAL, hal-01315717 / Harvested from HAL
Text on HAL
The authors give the necessary and sufficient conditions for the quadratic differential systems to possess two centers. Moreover, the condions are expressed with affine invariants.
Publié le : 1990-07-04
Classification:  quadratic differential systems,  centre-focus problem,  qualitative theory of differential systems,  [MATH]Mathematics [math] 
@article{hal-01315717,
     author = {Boularas, Driss and Vulpe, Nicolae and Sibirskii, Constantin Sergeivitch},
     title = {The problem of a center ``in the large'' for a  general quadratic system},
     journal = {HAL},
     volume = {1990},
     number = {0},
     year = {1990},
     language = {ru},
     url = {http://dml.mathdoc.fr/item/hal-01315717}
}

Boularas, Driss; Vulpe, Nicolae; Sibirskii, Constantin Sergeivitch. The problem of a center “in the large” for a  general quadratic system. HAL, Tome 1990 (1990) no. 0, . http://gdmltest.u-ga.fr/item/hal-01315717/