@article{CMUC_1997__38_1_a15,
     author = {Tkachuk, Vladimir V.},
     title = {Some non-multiplicative properties are $l$-invariant},
     journal = {Commentationes Mathematicae Universitatis Carolinae},
     pages = {169--175},
     publisher = {mathdoc},
     volume = {38},
     number = {1},
     year = {1997},
     mrnumber = {1455481},
     zbl = {0886.54005},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/CMUC_1997__38_1_a15/}
}