@article{10_21136_CMJ_1990_102410,
     author = {Niederle, Josef},
     title = {Transitivity of principal tolerances is not a {Mal'cev} property},
     journal = {Czechoslovak Mathematical Journal},
     pages = {563--565},
     publisher = {mathdoc},
     volume = {40},
     number = {4},
     year = {1990},
     doi = {10.21136/CMJ.1990.102410},
     mrnumber = {1084892},
     zbl = {0739.08004},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.21136/CMJ.1990.102410/}
}