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                \begin{document}$${\widehat{K}}^{\text {R}}_{\mu , \nu , \sharp }(\mathbf{p},\mathbf{q})$$\end{document}$, $\documentclass[12pt]{minimal}
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                \begin{document}$${\widehat{S}}^{\text {R}}_{j, \sharp }(\mathbf{p},\mathbf{q})$$\end{document}$ exist in $\documentclass[12pt]{minimal}
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                \begin{document}$$B_{\varepsilon }(\mathbf{0})\times B_\varepsilon (\mathbf{0})$$\end{document}$, and that they are of class $\documentclass[12pt]{minimal}
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                \begin{document}$$C^{3}$$\end{document}$ in this domain. Then:$$\documentclass[12pt]{minimal}
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                \begin{document}$$\begin{aligned} \frac{\partial }