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.
y = cons($1, $6) <= sub($5, $1) = $3, ssp($4, $3) = $6, ssp($4, $5) = y:
For all conditions c 'tcap(c.lhs)' is unifiable with c.rhs.