Prosenjit Bose Paz Carmi Mathieu Couture Anil Maheshwari Michiel H. M. Smid Norbert Zeh Geometric Spanners With Small Chromatic Number http://arxiv.org/abs/0711.0114 2007 CoRR abs/0711.0114 db/journals/corr/corr0711.html#abs-0711-0114 informal publication