@article{2715, author = {Henning, H.B.}, title = {Series approximations to powers of $\pi $ }, journal = {Portugaliae mathematica}, volume = {32}, year = {1973}, pages = {171-177}, zbl = {0257.65008}, mrnumber = {0315860}, language = {en}, url = {http://dml.mathdoc.fr/item/2715} }
Henning, H.B. Series approximations to powers of $\pi $ . Portugaliae mathematica, Tome 32 (1973) pp. 171-177. http://gdmltest.u-ga.fr/item/2715/