@article{SM_1985_51_1_a4,
     author = {B. M. Levitan},
     title = {On the closure of the set of finite-zone potentials},
     journal = {Sbornik. Mathematics},
     pages = {67--89},
     publisher = {mathdoc},
     volume = {51},
     number = {1},
     year = {1985},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1985_51_1_a4/}
}