@article{DAN_1996_351_3_a4,
     author = {I. F. Sivergina},
     title = {Invertibility and observability of evolution systems},
     journal = {Doklady Akademii Nauk},
     pages = {304--308},
     year = {1996},
     volume = {351},
     number = {3},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1996_351_3_a4/}
}