Slow vector optical solitons in a cold four-level inverted-Y atomic systemL. G. Si, W. X. Yang, X. Y. Lü, J. H. Li and X. X. YangEur. Phys. J. D, 55 1 (2009) 161-166DOI: https://doi.org/10.1140/epjd/e2009-00205-7