How to cite a reformulation of an older theorem? I'm currently in a position where I need a result from a paper where the formulation is a little unwieldy, in that it depends on some notations and concepts that aren't useful to my work. I found a reformulation of this result in a book (not a new result, just restating the same theorem in different words) that uses different notations and is easier for me to relate to what I'm doing.

Is it appropriate in this situation to cite both the original and the reformulation like this:

"Theorem X, formulation from Y, based on Z"?
I recommend restating the theorem in your own paper.  You can then say: "We now restate a theorem of X [citation], since in this context, it is more convenient to write it in different terms/notation. The version we give here is based on the book of Y [citation].  

Theorem: ....."