Jing-An Li Yue Wu Kin Keung Lai Ke Liu Reliability estimation and prediction of multi-state components and coherent systems. 93-98 2005 88 Rel. Eng. & Sys. Safety 1 http://dx.doi.org/10.1016/j.ress.2004.07.010 db/journals/ress/ress88.html#LiWLL05