Shai Ben-David Nadav Eiron Hans Ulrich Simon The Computational Complexity of Densest Region Detection. 22-47 2002 64 J. Comput. Syst. Sci. 1 https://doi.org/10.1006/jcss.2001.1797 db/journals/jcss/jcss64.html#Ben-DavidES02