@article{DAN_1974_215_5_a7,
     author = {V. F. Lazutkin and T. F. Pankratova},
     title = {Asymptotics of the width of gaps in the spectrum of the {Sturm--Liouville} operator with a periodic potential},
     journal = {Doklady Akademii Nauk},
     pages = {1048--1051},
     publisher = {mathdoc},
     volume = {215},
     number = {5},
     year = {1974},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1974_215_5_a7/}
}