Imaginärtransformation.
Geometrie Bd. 2, GDML_Books, (1968), p. 129 / Harvested from
Access to full text 
@article{PPN37649882X+dmdlog76,
     title = {Imagin\"artransformation.},
     booktitle = {Geometrie Bd. 2},
     series = {GDML\_Books},
     year = {1968},
     pages = {129},
     url = {http://dml.mathdoc.fr/item/PPN37649882X+dmdlog76}
}

 (ed.). Imaginärtransformation., in Geometrie Bd. 2, GDML_Books,  (1968), p. 129. http://gdmltest.u-ga.fr/item/PPN37649882X+dmdlog76/