@article{JDM_1931__40_145878,
     author = {Lothar Koschmieder},
     title = {Die neuere formale {Variationsrechnung.}},
     journal = {Jahresbericht der Deutschen Mathematiker-Vereinigung},
     pages = {109--132},
     publisher = {mathdoc},
     volume = {40},
     year = {1931},
     zbl = {0002.13901},
     url = {http://geodesic.mathdoc.fr/item/JDM_1931__40_145878/}
}