  We show that the knowledge of Dirichlet to Neumann map for rough $A$ and $q$
in $(-\Delta)^m +A\cdot D +q$ for $m \geq 2$ for a bounded domain in
$\mathbb{R}^n$, $n \geq 3$ determines $A$ and $q$ uniquely. This unique
identifiability is proved via construction of complex geometrical optics
solutions with sufficient decay of remainder terms, by using property of
products of functions in Sobolev spaces.
