@article{INTM_1977_14_a0,
     author = {M. Sh. Birman and M. Z. Solomyak},
     title = {Asymptotic properties of the spectrum of differential equations},
     journal = {Itogi nauki i tehniki. Seri\^a, Matemati\v{c}eskij analiz},
     pages = {5--58},
     publisher = {mathdoc},
     volume = {14},
     year = {1977},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/INTM_1977_14_a0/}
}