@article{MZ_1979__167_172842,
     author = {Rainer L\"owen},
     title = {Classification of {4-Dimensional} {Symmetric} {Planes.}},
     journal = {Mathematische Zeitschrift},
     pages = {137--160},
     publisher = {mathdoc},
     volume = {167},
     year = {1979},
     zbl = {0403.51012},
     url = {http://geodesic.mathdoc.fr/item/MZ_1979__167_172842/}
}