@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/}
}