Voir la notice de l'article provenant de la source European Digital Mathematics Library
@article{ELMA_1977__32_141200, author = {D. Kramer and Gerd Wegner}, title = {Ein ebenes {Extremalproblem.}}, journal = {Elemente der Mathematik}, pages = {109--112}, publisher = {mathdoc}, volume = {32}, year = {1977}, zbl = {0353.52003}, url = {http://geodesic.mathdoc.fr/item/ELMA_1977__32_141200/} }
D. Kramer; Gerd Wegner. Ein ebenes Extremalproblem.. Elemente der Mathematik, Tome 32 (1977), pp. 109-112. http://geodesic.mathdoc.fr/item/ELMA_1977__32_141200/