%0 Journal Article %A S. Ya. Yakubov %T Multiple completeness in the sense of M. V. Keldysh of root functions of elliptic boundary value problems with a polynomial spectral parameter %J Izvestiya. Mathematics %D 1987 %P 413-420 %V 28 %N 2 %U http://geodesic.mathdoc.fr/item/IM2_1987_28_2_a7/ %G en %F IM2_1987_28_2_a7