A. Friggeri, G. Chelius, and E. Fleury, Triangles to Capture Social Cohesion, 2011 IEEE Third Int'l Conference on Privacy, Security, Risk and Trust and 2011 IEEE Third Int'l Conference on Social Computing, 2011.
DOI : 10.1109/PASSAT/SocialCom.2011.169
URL : https://hal.archives-ouvertes.fr/inria-00608889

M. R. Garey and D. S. Johnson, Computers and Intractability: A Guide to the Theory of NP-Completeness INRIA Centre de recherche INRIA Grenoble ? Rhône-Alpes 655, W.H. Freeman, 1979.