then the symmetries can further be specified by parity (i.e. evenness or odd-ness). Since the L-point in rock-salt systems and the Γ-point in tetradymite systems are both preserved under crystal inversion, each state can be labeled by parity as in Figure , where "+" indicates even parity and "-" indicates odd parity. For example, in rock-salt SnSe (Figure ), the Se-p conduction band edge with Γ + 4 symmetry has even parity, whereas the secondary conduction band states with Γ - 4 and Γ - 5 ⊕ Γ - 6 symmetries have odd parity.