@article{10_21136_CMJ_1979_101639,
     author = {Svoboda, Karel},
     title = {Several new characterizations of the 2-dimensional sphere in $E^4$},
     journal = {Czechoslovak Mathematical Journal},
     pages = {573--583},
     publisher = {mathdoc},
     volume = {29},
     number = {4},
     year = {1979},
     doi = {10.21136/CMJ.1979.101639},
     mrnumber = {548220},
     zbl = {0435.53006},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.21136/CMJ.1979.101639/}
}