clabrd(3) on Linux
The text 5ee124c8ffe0, as Debian 4.0 (Etch), Debian 3.1 (Sarge) shipped it.
reduce the first NB rows and columns of a complex general m by n matrix A to upper or lower real bidiagonal form by a unitary transformation Q' * A * P, and returns the matrices X and Y which are needed to apply the transformation to the unreduced part of A