AFAIK, the CBOE Bitcoin Futures exchange uses a specifically-built index from Gemini exchange to track the BTC price. However, I cannot find a link. Where is t

AFAIK, the CBOE Bitcoin Futures exchange uses a specifically-built index from Gemini exchange to track the BTC price. However, I cannot find a link. Where is the link for the CBOE Bitcoin Futures index ? (Where did Bloomberg get the index data from? https://www.bloomberg.com/news/articles/2017-12-10/bitcoin-futures-trading-opens-bringing-crypto-to-wall-street https://www.bloomberg.com/news/articles/2017-12-10/bitcoin-f...)