Q. M. Zhang, M. An, S. K. Yuan, Y. Wu, D. Wu, J. L. Luo, N. L. Wang, Wei Bao, Y. N. Wang. Phonon softening and forbidden mode in Na0.5CoO2 observed by Raman scattering. Phys. Rev. B 77, 045110 (2008).
Q. M. Zhang, M. An, S. K. Yuan, Y. Wu, D. Wu, J. L. Luo, N. L. Wang, Wei Bao, Y. N. Wang. Phonon softening and forbidden mode in Na0.5CoO2 observed by Raman scattering. Phys. Rev. B 77, 045110 (2008).