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@article{MAN_1977__231_163047, author = {Man-Duen Choi and Tsit-Yuen Lam}, title = {Extremal {Positive} {Semidefinite} {Forms.}}, journal = {Mathematische Annalen}, pages = {1--18}, publisher = {mathdoc}, volume = {231}, year = {1977}, zbl = {0347.15009}, url = {http://geodesic.mathdoc.fr/item/MAN_1977__231_163047/} }
Man-Duen Choi; Tsit-Yuen Lam. Extremal Positive Semidefinite Forms.. Mathematische Annalen, Tome 231 (1977), pp. 1-18. http://geodesic.mathdoc.fr/item/MAN_1977__231_163047/