In principle a copyright resembles a patent. Each is the basis of a temporary monopoly. The most common copyrighted productions are books. Songs, pictures, magazines, and even news items may also be copyrighted. As in the case of patents, infringement is punishable by law. A copyright runs for twenty-eight years, though the author or his direct heirs may get an extension of fourteen years. No large per cent of copyrights is ever extended, however, for the sale of a book is likely to cease within a few years after it is first issued. Books written in foreign countries may now be copyrighted in the United States, though for years this privilege was refused; and this refusal accounts in large measure for the hostility of Charles Dickens and other English writers toward America.