@article{TMF_1993_94_1_a10,
     author = {Yu. G. Borisovich and B. M. Darinskii and O. V. Kunakovskaya},
     title = {Application of topological methods to estimate the number of longitudinal elastic waves in crystals},
     journal = {Teoreti\v{c}eska\^a i matemati\v{c}eska\^a fizika},
     pages = {146--152},
     publisher = {mathdoc},
     volume = {94},
     number = {1},
     year = {1993},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/TMF_1993_94_1_a10/}
}