@article{RM_1964_19_2_a0,
     author = {B. M. Levitan and M. G. Gasymov},
     title = {Determination of a~differential equation by two of its spectra},
     journal = {Trudy Matematicheskogo Instituta imeni V.A. Steklova},
     pages = {1--63},
     publisher = {mathdoc},
     volume = {19},
     number = {2},
     year = {1964},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/RM_1964_19_2_a0/}
}