@article{DM_1991_3_4_a1,
     author = {E. A. Mikheeva},
     title = {Classification of lower neighborhoods of closed classes in the lattice~$\mathcal L_k$},
     journal = {Diskretnaya Matematika},
     pages = {3--15},
     publisher = {mathdoc},
     volume = {3},
     number = {4},
     year = {1991},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DM_1991_3_4_a1/}
}