According to Section 5 (3) of the German Trademark Act (MarkenG), title protection applies to all works distributed in Germany. In the international German-speaking world, there are different regulations for titles and title protection, so if you are distributing internationally, you should find out exactly what the legal situation is in the target country. Austria, for example, is governed by Section 9 of the Unfair Competition Act (UWG).
The protected title may be mentioned and publicly referred to by others in connection with the designated work at any time. Once protection has been registered, only other works from the same business sector may no longer bear the same or an overly similar title. If there is any doubt about the commercial proximity of the designated works, you should contact the title owner directly. Authors and publishers of similar titles should set out in writing in advance what claims exist under what conditions.