@article{FAA_1981_15_1_a15,
     author = {A. Fraguela Collar},
     title = {Perturbation of a polyharmonic operator by a potential of delta-function type},
     journal = {Funkcionalʹnyj analiz i ego prilo\v{z}eni\^a},
     pages = {86--87},
     publisher = {mathdoc},
     volume = {15},
     number = {1},
     year = {1981},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/FAA_1981_15_1_a15/}
}