@article{AM2_1977__15_136645,
     author = {Z. Ditzian},
     title = {Note on {Hille's} question.},
     journal = {Aequationes mathematicae},
     pages = {143--144},
     publisher = {mathdoc},
     volume = {15},
     year = {1977},
     zbl = {0367.26005},
     url = {http://geodesic.mathdoc.fr/item/AM2_1977__15_136645/}
}