科研之友
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摘要
<正>Let V={a1,a2,...,an} be a finite set with n≥2 and Pn（V）the set of all primitive binary relations on V.For Q∈Pn（V）,denote by G（Q）the directed graph corresponding to Q. For positive integer d≤n,let Pn（V,d）={Q:Q∈Pn（V）and G（Q）contains exactly d loops}.In this paper,it is proved that the set of common consequent indices of binary relations in Pn（V,d） is {1,2,...,n-「d/2」}.Furthermore,the minimal extremal binary relations are described.
