I don't know whether it refers to propositional logic or the constructive proof in the reasoning theory of first-order logic. There are some in the textbook, which are clearly written, UI,

UG，

For example,

Engineering index

Equivalence refers to the introduction or elimination rules of quantifiers (different textbooks may have different notation), and you can find it by looking through the books. If you have specific questions that you can't do, you can bring them up for discussion.