@article{PFMT_2022_1_a13,
     author = {A. P. Starovoitov},
     title = {Polyorthogonal systems of functions},
     journal = {Problemy fiziki, matematiki i tehniki},
     pages = {89--93},
     publisher = {mathdoc},
     number = {1},
     year = {2022},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/PFMT_2022_1_a13/}
}