8Lin Yi, Liu Sifeng. Several programming models with unascertained parameters and their application[J]. Journal of Multi-Criteria Decision Analysis. 1999,8(1):206~220.
9Liu Sifeng. On perron-frobenius theorem of grey nonnegative matrix[J]. The Journal of Grey System,1989,1(2):157~166.
10Liu Sifeng. The three axioms of buffer operator and their application[J]. The Journal of Grey System,1991,3(1):39~48.