Each occurrence .i#k/ in a component of !.u/ represents either the node u itself (i D 0), or the kth block of some direct dependent ui of u (i ¤ 0), in which case we proceed recursively: The root node of a dependency structure has only one block.
to linearize a tree t , we only need to linearize the first block of the tree's root node: lin.t/ D lin.