@article{BAG_1986__21_138327,
     author = {G. GEISE},
     title = {Tangentenvierecke von {Kreisen}},
     journal = {Beitr\"age zur Algebra und Geometrie},
     pages = {83--90},
     publisher = {mathdoc},
     volume = {21},
     year = {1986},
     url = {http://geodesic.mathdoc.fr/item/BAG_1986__21_138327/}
}