Where i can find any proof of next theorem?


Theorem of Ostrowski: Let $\sum\_{n=0}^{\infty}a\_nz^n$ be a power series with radius of convergence 1, which is analytically continuable beyond unit disk. Then the power series is overconvergent if it possesses Hadamard-Ostrowski gaps.



Where i can find the proof of Ostrowski theorem
In English, in the book by P. Dienes, The Taylor series, Dover, NY, 1957.
In German: in the original A. Ostrowski's paper.


