@article{AA_2004_16_5_a1,
     author = {V. V. Zhikov},
     title = {On gaps in the spectrum of some divergence elliptic operators with periodic coefficients},
     journal = {Algebra i analiz},
     pages = {34--58},
     publisher = {mathdoc},
     volume = {16},
     number = {5},
     year = {2004},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/AA_2004_16_5_a1/}
}