I am writing up a paper and I use some very well known theorems, such as the Chinese remainder theorem and quadratic reciprocity, and want to state them so that the document is as self contained as possible. Consequently, I need to provide a citation for these theorems and I am wondering what would be the best way to go about doing that. Currently I am considering two options- the first where I have a sentence preceding the statement of the theorem explaining where the theorem appears in the source I'm citing and the second option I am considering is simply stating the theorem accompanied by a parenthetical citation. So those options as they stand would likely read something like
The following theorem appears in (source 1) as proposition $n$.
Theorem $k$: If (condition) then (property)
Theorem $k$: If (condition) then (property) [parenthetical citation]
Does either of these options seem ideal or is there a better way I have not thought of to reference a source in a situation like this one?