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@article{CM_1970__22_4_383_0, author = {Bryant, V. W.}, title = {The convexity of the subset space of a metric space}, journal = {Compositio Mathematica}, pages = {383--385}, publisher = {Wolters-Noordhoff Publishing}, volume = {22}, number = {4}, year = {1970}, mrnumber = {275293}, zbl = {0205.27102}, language = {en}, url = {http://geodesic.mathdoc.fr/item/CM_1970__22_4_383_0/} }
Bryant, V. W. The convexity of the subset space of a metric space. Compositio Mathematica, Tome 22 (1970) no. 4, pp. 383-385. http://geodesic.mathdoc.fr/item/CM_1970__22_4_383_0/