@article{MZ_1974__138_172084,
     author = {Oddvar Iden},
     title = {Natural {Bases} for {Subplanes} of {Free} {Completions.}},
     journal = {Mathematische Zeitschrift},
     pages = {97--110},
     publisher = {mathdoc},
     volume = {138},
     year = {1974},
     zbl = {0272.50023},
     url = {http://geodesic.mathdoc.fr/item/MZ_1974__138_172084/}
}