@article{SM_2016_207_5_a2,
     author = {Ya. M. Dymarskii and Yu. A. Evtushenko},
     title = {Foliation of the space of periodic boundary-value problems by hypersurfaces corresponding to fixed lengths of the $n$th spectral lacuna},
     journal = {Sbornik. Mathematics},
     pages = {678--701},
     publisher = {mathdoc},
     volume = {207},
     number = {5},
     year = {2016},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_2016_207_5_a2/}
}