gh¬g¬hg∧h¬(g∧h)¬g∨¬h¬(g∧h)⇔¬g∨¬hab¬a¬ba∧b¬(a∧b)¬a∨¬b¬(a∧b)⇔¬a∧¬b¬ef¬e¬fe∧f¬(e∧f)¬e∨¬f¬(e∧f)⇔¬e∨¬fcd¬c¬dc∧d¬(c∧d)¬c∨¬d¬(c∧d)⇔¬c∨¬d
