Pseudo- Riesz Bases

In~\cite{holub1994bases} Holub introduced the concept of near-Riesz bases, as frames that can be considered Riesz bases for computational purposes or that exhibit certain desirable properties of Riesz bases. In this paper, we introduce a generalization of near-Riesz bases that includes sequences which are not necessarily frames. We demonstrate that this broader class of sequences retains many of the desirable properties of near-Riesz bases and establish fundamental perturbation results for this new class.