@article{FAA_1989_23_3_a7,
     author = {V. N. Karpushkin},
     title = {Topology of the zeros of eigenfunctions},
     journal = {Funkcionalʹnyj analiz i ego prilo\v{z}eni\^a},
     pages = {59--60},
     publisher = {mathdoc},
     volume = {23},
     number = {3},
     year = {1989},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/FAA_1989_23_3_a7/}
}