Finally, the existence of this ambiguity is also confirmed by the contrast between full infinitives (with zu) and bare infinitives (without zu): Bare infinitives cannot form an embedded domain outside of the Vorfeld.
there are two different prosodies for (3a) (with or without detachment of das Buch 'the book' from zu lesen 'to read'), whereas only one prosody without detachment is permitted for (3b), although (3a) and (3b) have isomorphic dependency trees.