@article{10_4064_cm_46_2_257_262,
     author = {Rainer Walden},
     title = {Closed surfaces in four-spaces with non-vanishing normal curvature},
     journal = {Colloquium Mathematicum},
     pages = {257--262},
     publisher = {mathdoc},
     volume = {46},
     number = {2},
     year = {1982},
     doi = {10.4064/cm-46-2-257-262},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/cm-46-2-257-262/}
}