@article{MZ_1949__51_169071,
     author = {E. Kamke and G.G. LORENTZ},
     title = {\"Uber das {Dirichletsche} {Prinzip}},
     journal = {Mathematische Zeitschrift},
     pages = {217--232},
     year = {1949},
     volume = {51},
     zbl = {0030.15602},
     url = {http://geodesic.mathdoc.fr/item/MZ_1949__51_169071/}
}