(VAR x y z)
(RULES
not(and(x,y)) -> or(not(x),not(y))
not(or(x,y)) -> and(not(x),not(y))
and(x,or(y,z)) -> or(and(x,y),and(x,z))
)
(COMMENT Example 4.22 (Disjunctive Normal Form) in \cite{SK90})