Let \(L\) be a linear differential operator on a domain \(\Omega\subset \mathbb{R}^n\) of order \(m\) given by
\begin{equation*} Lu = \sum_{\lvert \alpha\rvert\le m} a_{\alpha}(x)\partial^{\alpha} u. \end{equation*}Let \(L\) be a linear differential operator on a domain \(\Omega\subset \mathbb{R}^n\) of order \(m\) given by
\begin{equation*} Lu = \sum_{\lvert \alpha\rvert\le m} a_{\alpha}(x)\partial^{\alpha} u. \end{equation*}