@article{CMJ_1998__48_4_a18,
     author = {Medvedev, N. Ya. and Morozova, S. V.},
     title = {On covers in the lattice of representable $\ell$-varieties},
     journal = {Czechoslovak Mathematical Journal},
     pages = {821--831},
     publisher = {mathdoc},
     volume = {48},
     number = {4},
     year = {1998},
     mrnumber = {1658210},
     zbl = {0952.06022},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/CMJ_1998__48_4_a18/}
}