Some notes on CE(S) production functions

We reconsider the CES production functions, focusing on their additive separability properties and the constraints these impose on dual elasticites of gross substitution and complementarity. In particular, we offer some alternative characterizations of the (standard) homogeneous cases that seem to have gone unnoticed, as far as we know. We also start exploring the cases of the (additively separable) non-homothetic technologies that satisfy constancy conditions for the mentioned dual elasticities