"Appearance of magnetic long-range order in the spin ladder compound La_1-xSr_xCuO_2.5" K. Ishii, A. Yamashita, K. Ohishi, J. Akimitsu, R. Kadono, N. Kobayashi, M. Takano, and Z. Hiroi, Physica B 289-290, 165-167 (2000).