@article{MASLO_1970__20_3_a1,
     author = {Havel, V\'aclav},
     title = {Incidence {Presystems}},
     journal = {Mathematica slovaca},
     pages = {166--171},
     publisher = {mathdoc},
     volume = {20},
     number = {3},
     year = {1970},
     mrnumber = {0305230},
     zbl = {0205.50102},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/MASLO_1970__20_3_a1/}
}