Let $U \subset \mathbb{R}^n$ be open, let $m \in \mathbb{R}$, and let $b: U \times \mathbb{R}^n \to \mathbb{C}$ satisfy $b \in S^m_{1,0}(U \times \mathbb{R}^n)$. If $x,y \in U$ and the line segment
is a symbol of order $m$ in the $\xi$ variable: for every multi-index $\beta \in \mathbb{N}_0^n$ there is a constant $C_{\alpha,\beta,x,y}>0$ such that