Trademark protection for titles of musical works is also problematic. In the United States, titles of a single work are considered generic by the courts and the USPTO and may not be registered unless the title is used on a series of works. Similarly, titles of a single work are considered descriptive by the courts and will not be protected unless the owner can establish that the title has acquired secondary meaning, namely, that the title is sufficiently well known that consumers associate it with a particular author's work. A similar rule applies to names of musical tours.