Xi Chen Seyoung Kim Qihang Lin Jaime G. Carbonell Eric P. Xing Graph-Structured Multi-task Regression and an Efficient Optimization Method for General Fused Lasso http://arxiv.org/abs/1005.3579 2010 CoRR abs/1005.3579 db/journals/corr/corr1005.html#abs-1005-3579