Tolkien authorized a paperback edition of "The Hobbit" in 1961, though that edition was never made available outside the U.K. Eventually, he supported paperback editions of "The Lord of the Rings" and several of his other texts, but whether he was persuaded to do so by the sales of the Ace editions is unknown. In any case, Ace was forced to cease publishing the unauthorized edition and to pay Tolkien for their sales following a grass-roots campaign by Tolkien's U.S. fans. A 1993 court determined that the copyright loophole suggested by Ace Books was invalid and its paperback edition was found to have been a violation of copyright under U.S. law(at this time, the U.S. had yet to join the International Copyright Convention, and most laws on the books existed to protect domestic creations from foreign infringement. Houghton Mifflin was technically in violation of the law when they exceeded their import limits and failed to renew their interim copyright). In the "Locus" obituary for Donald Wollheim, however, more details emerge: