... of oblique dual frames. Thevectorgkis a dual vector in W and gkis an oblique dual vector in V .In case the equivalent condit ions are satisfied, {gk}∞k=1is an oblique dual frame of { ... an oblique dual frame of { fk}∞k=1on V [10, 20–22]iff=∞k=1f , gkfk, ∀ f ∈ W . (13)The terminology oblique dual frame originates from the re-lation of these frames with oblique ... obtained a complete characterization of the oblique dual frames associated with a frame for a subspace of aHilbert space. Compared to the use of the classical dual frame, this leads to considerable...