@article{10_21136_CMJ_1992_128356,
     author = {Baxley, J. V. and Chapman, R. O.},
     title = {A criterion for discrete spectra of partial differential operators},
     journal = {Czechoslovak Mathematical Journal},
     pages = {403--414},
     publisher = {mathdoc},
     volume = {42},
     number = {3},
     year = {1992},
     doi = {10.21136/CMJ.1992.128356},
     mrnumber = {1179303},
     zbl = {0784.35067},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.21136/CMJ.1992.128356/}
}