@article{MASLO_1989__39_4_a2,
     author = {Duda, Jarom{\'\i}r},
     title = {Principal congruence relations and principal tolerances on varieties of lattices},
     journal = {Mathematica slovaca},
     pages = {365--369},
     publisher = {mathdoc},
     volume = {39},
     number = {4},
     year = {1989},
     mrnumber = {1094759},
     zbl = {0753.06005},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/MASLO_1989__39_4_a2/}
}