(VAR x y z)
(RULES
or(x,x) -> x
and(x,x) -> x
not(not(x)) -> x
not(and(x,y)) -> or(not(x),not(y))
not(or(x,y)) -> and(not(x),not(y))
)
(COMMENT Example 2.33 (Disjunctive Normal Form) in \cite{SK90})