@article{DAN_1957_114_3_a14,
     author = {A. Halanay and Sh. Shandor},
     title = {Sturm type theorems for self-conjugate systems of higher order differential equations},
     journal = {Doklady Akademii Nauk},
     pages = {506--507},
     publisher = {mathdoc},
     volume = {114},
     number = {3},
     year = {1957},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1957_114_3_a14/}
}