  In this chart, systems are given by the list of their axioms. So, for example \(\mathbf{M4B}\) is the result of adding \((M)\), (4) and \((B)\) to \(\bK\). In boldface, we have indicated traditional names of some systems. When system \(\mathbf{S}\) appears below and/or to the left of \(\mathbf{S}'\) connected by a line, then \(\mathbf{S}'\) is an extension of \(\mathbf{S}\). This means that every argument provable in \(\mathbf{S}\) is provable in \(\mathbf{S}'\), but \(\mathbf{S}\) is weaker than \(\mathbf{S}'\), i.e. not all arguments provable in \(\mathbf{S}'\) are provable in \(\mathbf{S}\).