As discussed in the literature, the importance of each contribution to the total NSCD is modulated by the size of the energy denominators. The denominators in the B K,a SOS are never smaller than the relative energy of the first excited state, and will progressively increase as energetically higher excited states are considered in the SOS. On the other hand, the energy difference between two excited states in the denominator of the dispersive terms can become very small and result in a very large contribution from this type of term, even dominant in the case of very close-lying excited states. Also, since the B K term is a scalar triple product, i.e., it contains the Levi-Civita tensor, and the PSO operator is imaginary, the dispersive contributions from a pair of excited states k and m to each other's NSCD signal will be identical in magnitude but of opposite sign. Thus, energetically close pairs of excited states may contribute to the NSCD spectrum with a bisignate feature if the contribution to B K,d due to the interaction of the two states is dominant in the SOS. In MCD, this feature is referred to as a pseudo-A term. Since ĥpso and μ are one-electron operators, their matrix elements between two excited states, ⟨k| Ô|m⟩, approximately become