Neeldhara Misra Geevarghese Philip Venkatesh Raman Saket Saurabh Somnath Sikdar FPT Algorithms for Connected Feedback Vertex Set http://arxiv.org/abs/0909.3180 2009 CoRR abs/0909.3180 db/journals/corr/corr0909.html#abs-0909-3180 informal publication