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@article{CM_1980__42_3_391_0, author = {Sierksma, Gerard}, title = {Convexity on unions of sets}, journal = {Compositio Mathematica}, pages = {391--400}, publisher = {Sijthoff et Noordhoff International Publishers}, volume = {42}, number = {3}, year = {1980}, mrnumber = {607378}, zbl = {0454.52001}, language = {en}, url = {http://geodesic.mathdoc.fr/item/CM_1980__42_3_391_0/} }
Sierksma, Gerard. Convexity on unions of sets. Compositio Mathematica, Tome 42 (1980) no. 3, pp. 391-400. http://geodesic.mathdoc.fr/item/CM_1980__42_3_391_0/