http://coinmamailtcrg7fw6uorut3d35bk35rtmntkrtb4fgeov6pefvfutqd.onion/blog/when-to-buy-bitcoin-a-history-of-bitcoin-market-cycles
This suggests people who have thus far employed the strategy to buy Bitcoin and hodl have historically made a sound choice. Secondly, the rainbow chart gives us a rough guide for determining when Bitcoin is under, over, or fairly valued. When price languishes along the lower, blue edge of the rainbow, Bitcoin is undervalued, the BTC price is low, and it’s a good time to buy Bitcoin.