Voir la notice de l'article provenant de la source European Digital Mathematics Library
@article{MOMA_1972__76_177596, author = {Su-Shing Chen}, title = {The {Schwarz} {Lemma} and the {Hadamard} {Three-Spheres} {Theorem} in {Hilbert} {Spaces.}}, journal = {Monatshefte f\"ur Mathematik}, pages = {218--221}, publisher = {mathdoc}, volume = {76}, year = {1972}, zbl = {0241.58003}, url = {http://geodesic.mathdoc.fr/item/MOMA_1972__76_177596/} }
Su-Shing Chen. The Schwarz Lemma and the Hadamard Three-Spheres Theorem in Hilbert Spaces.. Monatshefte für Mathematik, Tome 76 (1972), pp. 218-221. http://geodesic.mathdoc.fr/item/MOMA_1972__76_177596/