@article{PIM_1971_N_S_12_26_a7,
     author = {Charles H. Heiberg},
     title = {Functions {With} {Asymptotically} {Infinite} {Differences}},
     journal = {Publications de l'Institut Math\'ematique},
     pages = {45 },
     publisher = {mathdoc},
     volume = {_N_S_12},
     number = {26},
     year = {1971},
     url = {http://geodesic.mathdoc.fr/item/PIM_1971_N_S_12_26_a7/}
}