dlatrd(3) on Linux
The text 4be47ab00ba3, as Debian 4.0 (Etch), Debian 3.1 (Sarge) shipped it.
reduce NB rows and columns of a real symmetric matrix A to symmetric tridiagonal form by an orthogonal similarity transformation Q' * A * Q, and returns the matrices V and W which are needed to apply the transformation to the unreduced part of A