Improved approximation of the largest common subtree of two unordered trees of bounded height

We present a polynomial time 1.5h-approximation algorithm for the problem of finding the largest common subtree between two rooted, labeled, and unordered trees of height at most h, where a tree S is called a subtree of a tree T if S is obtained from T by deletion of some nodes in T. This result improves the previous 2h-approximation algorithm.