= Endpoint-false disjunctive normal form
A <propositional formula> false on the all-true and all-false <Boolean valuations> has a <disjunctive normal form> in which every <minterm> contains a positive <literal> and a negative <literal>. Grouping the positive <propositional variables> into $C$ and the negated <propositional variables> into the <negation> of a <logical disjunction> $D$ writes each <minterm> as $\neg(C\to D)$. <De Morgan's laws> therefore give the <negation> of a <logical conjunction> of such <logical implications>. For a <contradiction> use $\neg(p\to p)$.
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