@article{AL_1983_22_1_a3,
     author = {N. Ya. Medvedev},
     title = {Coverings in a lattice of $l$-varieties},
     journal = {Algebra i logika},
     pages = {53--60},
     publisher = {mathdoc},
     volume = {22},
     number = {1},
     year = {1983},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/AL_1983_22_1_a3/}
}