Cross-Gram Matrix associated to two sequences in Hilbert spaces

Elnaz Osgooei, Asghar Rahimi

The conditions for sequences $\{f_k{\}}_{k=1}^{\infty }$ and $\{g_k{\}}_{k=1}^{\infty }$ being Bessel sequences, frames or Riesz bases, can be expressed in terms of the so-called cro…