Agreement of classical Kubo theory with the infrared dispersion curves n(ω) of ionic crystals F. Gangemi, A. Carati, L. Galgani, R. Gangemi and A. Maiocchi EPL, 110 4 (2015) 47003 Published online: 29 May 2015 DOI: 10.1209/0295-5075/110/47003