Jeongseon Baek, Dong-Soo Kim, Young-Ho Kim. A Characterization of the Unit Sphere. The American Mathematical Monthly, 110(9):830-833, 2003. [doi]
@article{BaekKK03, title = {A Characterization of the Unit Sphere}, author = {Jeongseon Baek and Dong-Soo Kim and Young-Ho Kim}, year = {2003}, url = {http://www.jstor.org/stable/3647802}, researchr = {https://researchr.org/publication/BaekKK03}, cites = {0}, citedby = {0}, journal = {The American Mathematical Monthly}, volume = {110}, number = {9}, pages = {830-833}, }