@article{GDZPPN002330024, title = {Tautness and Lie Sphere Geometry.}, journal = {Mathematische Annalen}, volume = {277}, year = {1987}, pages = {381-400}, zbl = {0635.53029}, url = {http://dml.mathdoc.fr/item/GDZPPN002330024} }
Cecil, Thomas E.; Chern, Shiing-Shen. Tautness and Lie Sphere Geometry.. Mathematische Annalen, Tome 277 (1987) pp. 381-400. http://gdmltest.u-ga.fr/item/GDZPPN002330024/