@article{DM_1989_1_3_a9,
     author = {S. S. Marchenkov},
     title = {Finite initial segments of the upper semilattice of finite-automaton degrees},
     journal = {Diskretnaya Matematika},
     pages = {96--103},
     publisher = {mathdoc},
     volume = {1},
     number = {3},
     year = {1989},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DM_1989_1_3_a9/}
}