Chadi Kari Yoo Ah Kim Seungjoon Lee Alexander Russell Minho Shin Soft Edge Coloring. 189-203 2007 conf/approx/2007 APPROX-RANDOM http://dx.doi.org/10.1007/978-3-540-74208-1_14 db/conf/approx/approx2007.html#KariKLRS07