@article{UFA_2017_9_4_a0,
     author = {M. K. Arabov and E. M. Mukhamadiev and I. D. Nurov and Kh. I. Sobirov},
     title = {Existence tests for limiting cycles of second order differential equations},
     journal = {Ufa mathematical journal},
     pages = {3--11},
     publisher = {mathdoc},
     volume = {9},
     number = {4},
     year = {2017},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/UFA_2017_9_4_a0/}
}