Mining for trees in a graph is NP-complete

Of course, the even more general problem where the pattern is a graph is already well-known to be NP-complete, as it contains the well-known NP-complete Subgraph Isomorphism problem as the special case k = 1. We thus see here that restricting to tree patterns does not lower the worst-case complexity. The NP-completeness of Disjoint Occurrences of T3 follows immediately from the NP-completeness of the following problem: (a graph is called cubic if every node has degree 3, i.e., has edges to precisely 3 other nodes)