%0 Journal Article %A S. B. Sorokin %T The substantiation of the method of two-sided approximations for eigenvalues of the second-order elliptic operator %J Sibirskij žurnal vyčislitelʹnoj matematiki %D 2001 %P 61-84 %V 4 %N 1 %I mathdoc %U http://geodesic.mathdoc.fr/item/SJVM_2001_4_1_a6/ %G ru %F SJVM_2001_4_1_a6