%0 Journal Article %A V. V. Dyakin %A S. I. Petrukhnovskii %T On discreteness of the spectrum of some operator sheaves associated with a periodic Schrödinger equation %J Teoretičeskaâ i matematičeskaâ fizika %D 1988 %P 94-102 %V 74 %N 1 %U http://geodesic.mathdoc.fr/item/TMF_1988_74_1_a7/ %G ru %F TMF_1988_74_1_a7