Voir la notice de l'article provenant de la source European Digital Mathematics Library
@article{PORMA_1973__32_3_115205, author = {Henning, H.B.}, title = {Series approximations to powers of $\pi $}, journal = {Portugaliae mathematica}, pages = {171--177}, publisher = {mathdoc}, volume = {32}, number = {3}, year = {1973}, mrnumber = {0315860}, zbl = {0257.65008}, language = {en}, url = {http://geodesic.mathdoc.fr/item/PORMA_1973__32_3_115205/} }
Henning, H.B. Series approximations to powers of $\pi $. Portugaliae mathematica, Tome 32 (1973) no. 3, pp. 171-177. http://geodesic.mathdoc.fr/item/PORMA_1973__32_3_115205/