I just noticed this question that seems a dupe.
I have voted it as so, but one more thing caught my eye: one of the answers in the dupe is the exact copy of an answer in the original question (see here). How we should treat this? actually the copied answer provided a source... but I still believe that it should at least be reworded. Also to consider that if the 'copy-poster' founded the answer in another question on the same site, it probably would be better to mark the question as a dupe.
I am wondering what the common opinion is when working out such cases.