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@article{ELMA_1985__40_141358, author = {J. Simonis and J. de van de Craats}, title = {Coordinate free definitions of cross ratio.}, journal = {Elemente der Mathematik}, pages = {63--68}, publisher = {mathdoc}, volume = {40}, year = {1985}, zbl = {0569.51003}, url = {http://geodesic.mathdoc.fr/item/ELMA_1985__40_141358/} }
J. Simonis; J. de van de Craats. Coordinate free definitions of cross ratio.. Elemente der Mathematik, Tome 40 (1985), pp. 63-68. http://geodesic.mathdoc.fr/item/ELMA_1985__40_141358/