Three theorems on products of power series
Compositio Mathematica, Tome 14 (1959-1960) , pp. 41-49.
@article{CM_1959-1960__14__41_0,
     author = {Ostrowski, A. M.},
     title = {Three theorems on products of power series},
     journal = {Compositio Mathematica},
     pages = {41--49},
     publisher = {Kraus Reprint},
     volume = {14},
     year = {1959-1960},
     zbl = {0092.29303},
     mrnumber = {107113},
     language = {en},
     url = {archive.numdam.org/item/CM_1959-1960__14__41_0/}
}
Ostrowski, A. M. Three theorems on products of power series. Compositio Mathematica, Tome 14 (1959-1960) , pp. 41-49. http://archive.numdam.org/item/CM_1959-1960__14__41_0/