@article{CMH_1959__33_139175,
     author = {Woldemar Barthel},
     title = {Zur isodiametrischen und isoperimetrischen {Ungleichung} in der {Relativgeometrie.}},
     journal = {Commentarii mathematici Helvetici},
     pages = {241--257},
     publisher = {mathdoc},
     volume = {33},
     year = {1959},
     zbl = {0091.35602},
     url = {http://geodesic.mathdoc.fr/item/CMH_1959__33_139175/}
}