Credit: Pokémon
[글로벌 현장을 가다/김철중]‘미니 금괴’부터 ‘콩알 금’까지… 中 달구는 ‘바이 골드’ 열기，详情可参考电影
。PDF资料是该领域的重要参考
There is a special form for boolean formulas called "Conjunctive Normal Form" (CNF). A problem in this form consists of clauses connected with and operators, where each clause only contains variables connected with or operators. The variables can appear negated, but only variables can be directly negated, something like !(a && b) is not allowed. An example boolean formula in CNF form is:
FT App on Android & iOS，这一点在PDF资料中也有详细论述