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@article{PORMA_1981__40_4_115473, author = {Gupta, V.P.}, title = {Functions with negative coefficients}, journal = {Portugaliae mathematica}, pages = {439--448}, publisher = {mathdoc}, volume = {40}, number = {4}, year = {1981}, mrnumber = {0836107}, zbl = {0585.30015}, language = {en}, url = {http://geodesic.mathdoc.fr/item/PORMA_1981__40_4_115473/} }
Gupta, V.P. Functions with negative coefficients. Portugaliae mathematica, Tome 40 (1981) no. 4, pp. 439-448. http://geodesic.mathdoc.fr/item/PORMA_1981__40_4_115473/