@article{MZM_1971_9_6_a7,
     author = {V. G. Mishin},
     title = {The negative part of the spectrum of the operator $(-1)^m\Delta^mu+qu$},
     journal = {Matemati\v{c}eskie zametki},
     pages = {677--686},
     publisher = {mathdoc},
     volume = {9},
     number = {6},
     year = {1971},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1971_9_6_a7/}
}