# reference request – Hahn’s theorem on ordered fields

There is a theorem attributed to Hahn that every ordered field $$F$$ containing $$mathbb R$$ is a subfield of a formal power series field $$mathbb R[[X^Gamma]]$$, where $$Gamma$$ is an ordered abelian group. Can you give a nice reference in English for a proof of this theorem? Or if it is not too hard, please sketch a proof below.