According to the personal library network, there is no need to apply for classes in Liu Yi. Many people have been studying Liu Yi for many years, and the more they learn, the more confused they become, and even interrupted. Blind study is not recommended.

The prediction of six hexagrams and eight diagrams is a law summarized by the ancients by observing the operation law of nature. Originated from Fang Jing's Najia system in the Western Han Dynasty.