Nested CES Production Function
Consider the CES production function over four goods defined as follows:
$$ x = (\alpha j^{\gamma} + k^{\gamma})^{1/\gamma}$$
$$ y = (\delta l^{\beta} + m^{\beta})^{1/\beta }$$
$$ z = (\zeta x^{\xi} + y^{\xi})^{1/\xi }$$
If $\gamma$ is near one then $j$ and $k$ are near perfect substitutes. If $\beta$ is near one then $l$ and $m$ are near perfect substitutes. If $\xi$ is a large negative value then the composite goods $x$ and $y$ are near perfect complements