@article{MZ_1971__119_171480,
     author = {Oddvar Iden},
     title = {Free {Planes.} {IV.}},
     journal = {Mathematische Zeitschrift},
     pages = {111--114},
     publisher = {mathdoc},
     volume = {119},
     year = {1971},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/MZ_1971__119_171480/}
}