@article{SM_1992_71_1_a7,
     author = {Yu. E. Karpeshina},
     title = {Perturbation theory formulas for the {Schr\"odinger} equation with a~nonsmooth periodic potential},
     journal = {Sbornik. Mathematics},
     pages = {101--123},
     publisher = {mathdoc},
     volume = {71},
     number = {1},
     year = {1992},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1992_71_1_a7/}
}