= Robin half-line Green function from left and right solutions
{c}
{title2=$G(x,\xi)=u(\min(x,\xi))v(\max(x,\xi))/W(\xi)$}
For a monic second-order operator, choose a homogeneous solution $u$ satisfying the left <Robin boundary condition> and a solution $v$ satisfying the right decay condition. With $W=uv'-u'v\ne0$, the displayed kernel is continuous and its first derivative has jump one. It therefore satisfies $LG=\delta$ and the two boundary conditions. The operator's first derivative term generally makes $W$ nonconstant and the resulting <Green function> nonsymmetric in the unweighted variables.
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