I'm searching for a problem book in complex analysis published by MIR. It was recommended by my professor (when I asked for a Demidovich equivalent in the field), but he did not remember the exact name (possibly "Ejercicios de Analise Complexa" - Exercises in Complex Analysis) nor the author. He said the book was quite difficult, it don't have applications and he mentioned a particular and hard problem involving a construction of a Riemannian surface.
Edit: The problem of the construction of a Riemannian surface has a infinity product of functions.