Local quasinilpotence and common invariant subspaces
  In this article we obtain some positive results about the existence of a common nontrivial invariant subspace for $N$-tuples of not necessarily commuting operators on Banach spaces with a Schauder basis. The concept of joint quasinilpotence plays a basic role. Our results complement recent work by Kosiek \cite{6} and Ptak \cite{8}. 
A Fern\'andez Valles