Directed graphs of inner translations of semigroups
          Araújo, João; Bentz, Wolfram; Janusz Konieczny  
          
          Semigroup Forum, 94(3) (2017), 650-673  
          https://link.springer.com/article/10.1007/s00233-016-9821-x  
           
          A mapping $\al\colon S\to S$ is called a \emph{Cayley function} if
 there exist an associative operation $\mu\colon S\times S\to S$ and an element $a\in S$ such that $\al(x)=\mu(a,x)$
 for every $x\in S$. The aim of the paper is to give a characterization of Cayley functions in terms of their directed graphs.
 This characterization is used to determine which elements of the centralizer of a permutation on a finite set
 are Cayley functions. The paper ends with a number of problems.
   
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