With regard to this question which was labeled a duplicate, I wish to understand how to best register my disagreement with that labeling. The alleged original question asks for a short proof of the result, while the current question asks for a particular derivation which anyone who understands the concept knows is not "short."
It seems the question has been reopened. (I suppose that it was thanks to your post on meta.)
Here is also link to the timeline of that question.
(I am posting this so that this question does not remain unanswered.)