1. Twin convergence regions for continued fractions;Cowling, V. F.;Bull. Amer. Math. Soc.,1944
2. J. Dieudonné, La théorie analytique des polynomes d’une variable, Memorial des Sciences Mathématiques, vol. 93, Paris, 1938.
3. Continued fractions with complex elements;Leighton, Walter;Duke Math. J.,1942