Effects of relative phase in an open ladder system without incoherent pumpingX. J. Fan, A. Y. Li, S. F. Tian, D. M. Tong, S. Q. Gong and Z. Z. XuEur. Phys. J. D, 42 3 (2007) 483-488DOI: https://doi.org/10.1140/epjd/e2007-00040-x