@article{JDM_1931__40_145896,
     author = {F. Kadner},
     title = {\"Uber {Isogonalsysteme} ebener {W-Kurven.}},
     journal = {Jahresbericht der Deutschen Mathematiker-Vereinigung},
     pages = {254--263},
     year = {1931},
     volume = {40},
     language = {de},
     url = {http://geodesic.mathdoc.fr/item/JDM_1931__40_145896/}
}