@article{ZNSL_2001_276_a4,
     author = {V. N. Dubinin and E. V. Kostyuchenko},
     title = {Extremal problems in the function theory associated with the $n$-fold symmetry},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {83--111},
     publisher = {mathdoc},
     volume = {276},
     year = {2001},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_2001_276_a4/}
}