@article{DAN_1990_315_5_a5,
     author = {S. V. Emel'yanov and S. K. Korovin and M. G. Nikitina and S. V. Nikitin},
     title = {Approximate controllability and observability of},
     journal = {Doklady Akademii Nauk},
     pages = {1052--1056},
     publisher = {mathdoc},
     volume = {315},
     number = {5},
     year = {1990},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1990_315_5_a5/}
}