@article{10_4064_ap_13_2_121_127,
     author = {J. Witkowski},
     title = {On a characterization of the {Euclidean} sphere},
     journal = {Annales Polonici Mathematici},
     pages = {121--127},
     publisher = {mathdoc},
     volume = {13},
     number = {2},
     year = {1963},
     doi = {10.4064/ap-13-2-121-127},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/ap-13-2-121-127/}
}