9Kun-Li Wen, John H Wu. The grey-fuzzy relational model and its application to welding flaw identification [J]. The Journal of Grey System, 1995,7 (4) : 331 - 338.
10Liu Xiaotao, Yong Qidong. Grey relation analysis of optimizing multi-objective complex alternatives: the 2order grey relational analysis [J]. The Journal of Grey System, 1997,9(4) :379 -385.
