@article{robnik:1980:eps,
    author = {Robnik, Marko},
     title = {An extremum property of the {$n$}-dimensional sphere},
   journal = {J. Phys. A},
  fjournal = {Journal of Physics. A. Mathematical and General},
    volume = {13},
      year = {1980},
    number = {10},
     pages = {L349–L351},
      issn = {0305-4470},
     coden = {JPHACS},
   mrclass = {49G05 (35P15)},
  mrnumber = {MR587734 (83b:49045)},
       doi = {10.1088/0305-4470/13/10/001}}