@article{MAN_1928__100_159301,
     author = {A. Haar},
     title = {\"Uber adjungierte {Variationsprobleme} und adjungierte {Extremalfl\"achen}},
     journal = {Mathematische Annalen},
     pages = {481--502},
     publisher = {mathdoc},
     volume = {100},
     year = {1928},
     language = {de},
     url = {http://geodesic.mathdoc.fr/item/MAN_1928__100_159301/}
}