@article{SMJ2_1999_25_1_a4,
     author = {Pyrih, Pavel},
     title = {On the sense preserving mappings in the {Helm} topology in the plane},
     journal = {Serdica Mathematical Journal},
     pages = {41--46},
     publisher = {mathdoc},
     volume = {25},
     number = {1},
     year = {1999},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SMJ2_1999_25_1_a4/}
}