@article{PFMT_2020_2_a14,
     author = {V. I. Mironenko and V. V. Mironenko},
     title = {The center-focus problem and reflecting function},
     journal = {Problemy fiziki, matematiki i tehniki},
     pages = {80--84},
     publisher = {mathdoc},
     number = {2},
     year = {2020},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/PFMT_2020_2_a14/}
}