Fig. 9From: Two metrics on rooted unordered trees with labelsA 2-level tree \(T_{12}\) (upper left), its level-2 completion \({\bar{T}}_{12}(2)\) (upper right) and its level-3 completion \({\bar{T}}_{12}(3)\) (lower). The level (Lv.) of each vertex is marked on the leftBack to article page