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. \cite{GNG13}, Theorem 9 does not apply. \cite{SMI95}, Corollary 4.7 or 5.3 do not apply. Some critical pairs are not trivial and ConCon could not decide whether those all are infeasible. 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.