Therese C. Biedl Stephane Durocher Holger H. Hoos Shuang Luan Jared Saia Maxwell Young Fixed-Parameter Tractability and Improved Approximations for Segment Minimization http://arxiv.org/abs/0905.4930 2009 CoRR abs/0905.4930 db/journals/corr/corr0905.html#abs-0905-4930 informal publication