“…We establish two sufficient conditions under which an involution monoid is nonfinitely based. By applying one of the sufficient conditions to the involution semigroups (T 2 (F), * ), (UT 2 (F), * ) and (UT ±1 2 (F), * ), we show that (T 2 (F), * ) and (UT 2 (F), * ) are nonfinitely based when char(F) 0, and (UT ±1 2 (F), * ) is nonfinitely based for any field F. Together with the results of [24], this shows that (T 2 (F), * ), (UT 2 (F), * ) and (UT ±1 2 (F), * ) are nonfinitely based for any field F.…”