let R be the TRS under consideration

h(f(f(_1))) -> h(f(g(f(_1)))) is in elim_R(R)
let r0 be the right-hand side of this rule
p0 = 0 is a position in r0
we have r0|p0 = f(g(f(_1)))
f(g(f(_2))) -> f(f(_2)) is in R
let l'0 be the left-hand side of this rule
theta0 = {_1/_2} is a mgu of r0|p0 and l'0

==> h(f(f(_1))) -> h(f(f(_1))) is in EU_R^1
let l be the left-hand side and r be the right-hand side of this rule
let p = epsilon
let theta = {}
let theta' = {}
we have r|p = h(f(f(_1))) and
theta'(theta(l)) = theta(r|p)
so, theta(l) = h(f(f(_1))) is non-terminating w.r.t. R

Termination disproved by the forward process
proof stopped at iteration i=1, depth k=4
3 rule(s) generated