@article{ZNSL_1988_169_a8,
     author = {Yu. E. Karpeshina},
     title = {The theory of perturbations for a polyharmonic operator with non-smooth periodic potential},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {76--83},
     publisher = {mathdoc},
     volume = {169},
     year = {1988},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_1988_169_a8/}
}