@article{SM_1985_52_2_a1,
     author = {A. A. Mal'tsev},
     title = {On the structure of families of immune, hyperimmune and hyperhyperimmune sets},
     journal = {Sbornik. Mathematics},
     pages = {301--313},
     publisher = {mathdoc},
     volume = {52},
     number = {2},
     year = {1985},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1985_52_2_a1/}
}