@article{TMF_2011_168_3_a15,
     author = {I. V. Stasyuk and O. V. Velichko},
     title = {Bose--Einstein condensation in the~excited band and the~energy spectrum of {the~Bose--Hubbard} model},
     journal = {Teoreti\v{c}eska\^a i matemati\v{c}eska\^a fizika},
     pages = {571--583},
     publisher = {mathdoc},
     volume = {168},
     number = {3},
     year = {2011},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/TMF_2011_168_3_a15/}
}