@article{MM2_1971__5_154056,
     author = {Dietmar Arlt},
     title = {Freudenthal-Invariante.},
     journal = {Manuscripta mathematica},
     pages = {1--18},
     year = {1971},
     volume = {5},
     language = {de},
     url = {http://geodesic.mathdoc.fr/item/MM2_1971__5_154056/}
}