@article{VUU_2021_31_1_a2,
     author = {O. S. Kostromina},
     title = {On two-frequency quasi-periodic perturbations of systems close to two-dimensional {Hamiltonian} ones with a double limit cycle},
     journal = {Vestnik Udmurtskogo universiteta. Matematika, mehanika, kompʹ\^uternye nauki},
     pages = {35--49},
     publisher = {mathdoc},
     volume = {31},
     number = {1},
     year = {2021},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/VUU_2021_31_1_a2/}
}