New longitudinal waves in electron-positron-ion quantum plasmasN.L. Tsintsadze, L.N. Tsintsadze, A. Hussain and G. MurtazaEur. Phys. J. D, 64 2-3 (2011) 447-452DOI: https://doi.org/10.1140/epjd/e2011-20332-8