Feedback Vertex Set (FVS) is NP-complete for general graphs. It is known to be NP-complete for degree-$8$ bounded graphs due to a reduction from vertex cover. The Wikipedia article says that it is poly-time solvable for degree-$3$ bounded graphs and is NP-complete for degree-$4$ bounded graphs. But I have not been able to find any proof for this anywhere. Is it true?
What is the minimum $d$ such that FVS in degree-$d$ bounded graphs is NP-complete?