@article{MZ_1972__126_171723,
     author = {Robert Liebler},
     title = {A {Characterization} of the {L\"uneburg} {Planes.}},
     journal = {Mathematische Zeitschrift},
     pages = {82--90},
     publisher = {mathdoc},
     volume = {126},
     year = {1972},
     zbl = {0229.50028},
     url = {http://geodesic.mathdoc.fr/item/MZ_1972__126_171723/}
}