If NP in BPP then NP equals RP I am looking for a reference to the fact that if NP is included in BPP then NP is equal to RP. See for instance these links:


https://cs.stackexchange.com/q/80509
http://www.inf.ed.ac.uk/teaching/courses/cmc/cw3_solns.pdf
https://www.csie.ntu.edu.tw/~lyuu/complexity/2011/20120103s.pdf


I know that this is folklore, but I'd still like to cite something that is published and where this would be properly proved.
An actual factual reference is 

K. Ko. Some observations on the probabilistic algorithms and NP-hard problems. Information Processing Letters, 14(1):39–43, 1982.

(When I first saw this result --- I don't remember where it was now --- it was called "Ko's Theorem". Googling suggests that another theorem has that name as well...)