@article{10_21136_CPM_1980_118069,
     author = {Svoboda, Karel},
     title = {Characterizations of the sphere in $E^4$ by means of the pseudoparallel mean curvature vector field},
     journal = {\v{C}asopis pro p\v{e}stov\'an{\'\i} matematiky},
     pages = {266--277},
     publisher = {mathdoc},
     volume = {105},
     number = {3},
     year = {1980},
     doi = {10.21136/CPM.1980.118069},
     mrnumber = {588677},
     zbl = {0435.53005},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.21136/CPM.1980.118069/}
}