$$ \newcommand{\tp}{\thinspace .} \newcommand{\x}{\boldsymbol{x}} \renewcommand{\u}{\boldsymbol{u}} \renewcommand{\v}{\boldsymbol{v}} \newcommand{\V}{\boldsymbol{V}} \newcommand{\baspsi}{\psi} \newcommand{\dx}{\, \mathrm{d}x} $$

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