@article{DAN_1965_165_3_a2,
     author = {M. A. Gol'dman and S. N. Krachkovskii},
     title = {The $d$-characteristic of a linear operator},
     journal = {Doklady Akademii Nauk},
     pages = {476--478},
     publisher = {mathdoc},
     volume = {165},
     number = {3},
     year = {1965},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1965_165_3_a2/}
}