n matrices $H_i \in \mathbb{R}^{m \times m}$, $i = 1, 2, ..., n$. He also observed that each $H_i$ can be written as $H_i = 4z_i z_i^T$ where $z_i \in \mathbb{R}^m$ for $i = 1, 2, ..., n$. It was also observed that $(z_i, z_j) = 0$ where $i \neq j$ and $(z_i, z_i) = 1$ for all $i = 1, 2, ..., n$.