8Barlow R E, Wu A S. Coherent Systems with Multistates Components[J].Math. of Operation Research, 1978, 37(3):275-281.
9Wu S M. Joint Importance of Multistate Systems[J]. Computers & Industrial Engineering, 2005, 49(1) : 63-75.
10Gao X I., Cui L R, Li J L. Analysis for Joint Importance of Components in a Coherent System[J]. European Journal of Operational Research, 2007, 182(1) : 282-299.