@article{DM_1997_9_4_a5,
     author = {E. E. Marenich},
     title = {The action of the automorphism group of a finite graded partially ordered set on levels},
     journal = {Diskretnaya Matematika},
     pages = {63--72},
     year = {1997},
     volume = {9},
     number = {4},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DM_1997_9_4_a5/}
}