“…It is clear from the discussion in Appendix A that if is the "part" of that annihilates , then consists of elementary Givens rotation matrices and satisfies (18) Furthermore, it is straightforward that Combining, (14), (15), and the input vector partition , we get (19) where the vector corresponds to the last elements of and is expressed as (20) Clearly, is the th-order a priori backward error vector, and consequently, can be interpreted as the th-order normalized a priori backward error vector. In addition, the nesting of vectors in (19) indicates that the th -element block of (16) corresponds to the th-order normalized a priori backward error vector for From (14), (16), and the input vector partition , we also obtain (21) where (22) is the th-order a priori normalized forward error vector.…”