@article{SM_1988_61_1_a16,
     author = {N. S. Nadirashvili},
     title = {Multiple eigenvalues of the {Laplace} operator},
     journal = {Sbornik. Mathematics},
     pages = {225--238},
     publisher = {mathdoc},
     volume = {61},
     number = {1},
     year = {1988},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1988_61_1_a16/}
}