Fischer, M., Lemmens, P., Els, G., Güntherodt, G., Sherman, E. Y., Morré, E., et al. (1999). Spin-gap behavior and charge ordering in α′-NaV2O5 probed by light scattering. Physical Review B, 60, 7284-7294. doi:10.1103/PhysRevB.60.7284.