(VAR x y z u)
(RULES
+(x,+(y,z)) -> +(+(x,y),z)
*(x,+(y,z)) -> +(*(x,y),*(x,z))
+(+(x,*(y,z)),*(y,u)) -> +(x,*(y,+(z,u)))
)
(COMMENT Example 2.5 (Associativity and Distributivity) in \cite{SK90})