 None of these systems is functionally complete: there are connectives not definable on the basis of C and N alone. Among those that are definable is possibility M: as early as 1921 Tarski showed that it could be defined as CNpp. In 1936 Słupecki showed that by adding a functor \(T\) specifiable as \(\tval{Tp} = \tfrac{1}{2}\) for all values of p, all connectives can be defined in Ł3. To axiomatize these functionally complete system the formulas