@article{10_1051_mmnp_20105402,
     author = {M. Sh. Birman and V. A. Sloushch},
     title = {Discrete {Spectrum} of the {Periodic} {Schr\"odinger} {Operator} with a {Variable} {Metric} {Perturbed} by a {Nonnegative} {Potential}},
     journal = {Mathematical modelling of natural phenomena},
     pages = {32--53},
     publisher = {mathdoc},
     volume = {5},
     number = {4},
     year = {2010},
     doi = {10.1051/mmnp/20105402},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.1051/mmnp/20105402/}
}