MAYBE

Proof:
ConCon could not decide confluence of the system.
\cite{ALS94}, Theorem 4.1 does not apply.
ConCon could not decide whether all critical pairs are joinable or not.
cons(y, cons(x, cons(x', $4))) = cons(y, cons($3, $4)) <= orient(y, $3) = pair(x, x'):
For all conditions c 'tcap(c.lhs)' is unifiable with c.rhs.
\cite{GNG13}, Theorem 9 does not apply.
\cite{SMI95}, Corollary 4.7 or 5.3 do not apply.