@article{SM_1991_70_2_a6,
     author = {A. S. Andreev},
     title = {Estimates of the spectrum of compact pseudodifferential operators in unbounded domains},
     journal = {Sbornik. Mathematics},
     pages = {431--443},
     publisher = {mathdoc},
     volume = {70},
     number = {2},
     year = {1991},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1991_70_2_a6/}
}