@article{05130556,
title = {Necessary conditions for existence of periodic solutions of a differential system.},
journal = {Matematichki Vesnik},
volume = {57},
year = {2005},
pages = {15-17},
zbl = {1114.34314},
language = {en},
url = {http://dml.mathdoc.fr/item/05130556}
}
Knežević-Miljanović, Julka. Necessary conditions for existence of periodic solutions of a differential system.. Matematichki Vesnik, Tome 57 (2005) pp. 15-17. http://gdmltest.u-ga.fr/item/05130556/