@article{AUCMP_1993__34_2_a6,
     author = {Grzegorek, E.},
     title = {On extensions of $\sigma$-fields of sets},
     journal = {Acta Universitatis Carolinae. Mathematica et Physica},
     pages = {47--49},
     publisher = {mathdoc},
     volume = {34},
     number = {2},
     year = {1993},
     mrnumber = {1282965},
     zbl = {0810.28001},
     language = {en},
     url = {https://geodesic-test.mathdoc.fr/item/AUCMP_1993__34_2_a6/}
}