"tree structures" . "Tree" . "tree representation" . "Hierarchical Tree" . . "tree hierarchy" . "Tree Map" . "trees" . "tree diagram" . . "tree diagrams" . "node\u2013link diagram" . . "tree structure" . "tree-structured" . . "tree-diagrams" . . . "Tree structure" . . . . . . . . "ancestors" . "branch out" . . "hierarchical tree" . "Tree structure" . "inverted-tree structure" . "hierarchical structure" . "Positional tree" . . "tree" .