Stavros Athanassopoulos Ioannis Caragiannis Christos Kaklamanis Maria Kyropoulou An Improved Approximation Bound for Spanning Star Forest and Color Saving. 90-101 2009 MFCS http://dx.doi.org/10.1007/978-3-642-03816-7_9 conf/mfcs/2009 db/conf/mfcs/mfcs2009.html#AthanassopoulosCKK09