4Chen Z Y, Ding D C. Variable minimal unsatisfiability. In: Theory and Applications of Models of Computation, 2006, LNCS 3959: 262- 273.
5Lau M F, Yu Y T. An extended fault class hierarchy for specification-based testing. ACM T Softw Eng Meth, 2005, 14:247-276.
6Chen Z Y, Xu B W, Nie C H. A detectability analysis of fault classes for Boolean specifications. In: 23rd Annual ACM Symposium on Applied Computing, 2008. 390-394.
7Ravi K, Somenzi F. Minimal assignments for bounded model checking. In: 10th International Conference on Tools and Algorithms for the Construction and Analysis of Systems, 2004. 31-45.
8Papadimitriou C H, Yannakakis M. The complexity of facets (and some facets of complexity). J Comput Syst Sci, 1984, 28:244-259.
9Kleine B H, Lettmann T. Propositional Logic: Deduction and Algorithms. London: Cambridge University Press, 1999.
10Umans C. The minimum equivalent DNF problem and shortest implicants. J Comput Syst Sci, 2001, 53:597-611.
