Drinfeld had said that quantum loop algebras can degenerate into Yangians.But i can not find any proof about that .Can anyone give me some reference about this question.

A great very recent paper on the subject is Yangians and quantum affine algebras by Gautam and ToledanoLaredo, where a stronger (and unexpected) form of Drinfeld's result is proved (and there are references to older works of course). 


A recent paper give a complete proof: 

