---- CR(R cup S)
---- [Klein and Hirokawa, 2012]
R:
f(f(x)) -> f(g(f(x)))
S:

CP_S(R):
f(f(g(f(___y23)))) -> f(g(f(f(___y23))))
CR(S):
see below.

---- CR(R)
---- [Hirokawa and Middeldorp, 2011]
R:

CPS'(R):

CP(R):