%0 Journal Article %A Baxley, J. V. %A Chapman, R. O. %T A criterion for discrete spectra of partial differential operators %J Czechoslovak Mathematical Journal %D 1992 %P 403-414 %V 42 %N 3 %I mathdoc %U http://geodesic.mathdoc.fr/articles/10.21136/CMJ.1992.128356/ %R 10.21136/CMJ.1992.128356 %G en %F 10_21136_CMJ_1992_128356