Denote by $S^m \left ( \mathbb{R}^k \times \mathbb{R}^n \right)$ the usual space of symbols. Now let $E$ be a Fréchet Space. We can then define $S^m \left ( \mathbb{R}^k \times \mathbb{R}^n; E \right)$ as the space of smooth functions $q:\mathbb{R}^k \times \mathbb{R}^n \to E $ which satisfy $ \sup_{z,\xi} || \partial_z^\alpha \left < \xi \right >^{|\beta|-m} \partial_\xi^\beta q ||_j < \infty$ for a family of seminorms $||\cdot||_j$ for $E$.
My question is: under which conditions can we say that $S^m \left ( \mathbb{R}^k \times \mathbb{R}^n; E \right)$ is isomorphic (via the natural map) to the completed projective tensor product $S^m \left ( \mathbb{R}^k \times \mathbb{R}^n \right) \hat \otimes E$?
I'm sure these things have been looked at before. Any suggestion on papers using them are welcome.