@article{CMUC_1990__31_4_a13,
     author = {Balcerzak, Marek},
     title = {On isomorphisms between $\sigma$-ideals on $\omega_1$},
     journal = {Commentationes Mathematicae Universitatis Carolinae},
     pages = {743--749},
     publisher = {mathdoc},
     volume = {31},
     number = {4},
     year = {1990},
     mrnumber = {1091371},
     zbl = {0722.04002},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/CMUC_1990__31_4_a13/}
}