@article{MZM_2007_81_4_a17,
     author = {E. A. Shiryaev and A. A. Shkalikov},
     title = {Regular and {Completely} {Regular} {Differential} {Operators}},
     journal = {Matemati\v{c}eskie zametki},
     pages = {636--640},
     publisher = {mathdoc},
     volume = {81},
     number = {4},
     year = {2007},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_2007_81_4_a17/}
}