(from
Fissore, Olivier and Gnaedig, Isabelle and Kirchner, Hélène. 
Outermost ground termination - Extended version. Technical Report A02-R-493
2002, LORIA, Nancy, France
)

(VAR x y)

(RULES
f(x,x)	-> f(i(x),g(g(x)))
f(x,y)	-> x
g(x)	-> i(x)
f(x,i(x))	-> f(x,x)
f(i(x),i(g(x)))	-> a
)