@techreport{TR-IC-01-12,
  number = {IC-01-12},
  author = {F. Larrión and C. P. de Mello and V. Neumann-Lara and A. Morgana and M. A. Pizaña},
  title = {The Clique Operator on Cographs and Serial Graphs},
  month = {October},
  year = {2001}, 
  institution = {Institute of Computing, University of Campinas},
  note = {In English, 12 pages.
    \par\selectlanguage{english}\textbf{Abstract}
      The {\bf clique graph} of a graph $G$ is the intersection graph $K(G)$ of
      the (maximal) cliques of $G$. The iterated clique graphs $K^{n}(G)$ are
      defined by $K^{0}(G)=G$ and $K^{i}(G)=K(K^{i-1}(G))$, where $i>0$ and $K$ is the
      clique operator. A {\bf cograph} is a graph with no induced subgraph
      isomorphic to $P_{4}$. In this article we describe the $K$-behaviour of
      cographs and give some partial results for the larger class of serial 
      (i.e.~complement-disconnected) graphs.
  }
}