        The detail of the picture was near-photographic quality, when he allowed for the roughness of the pages, although he was surprised that the writing under it seemed to have been written by hand, rather than printed by machine.  He looked a little more closely and discovered that what he had taken as a decorative border to the picture was in fact concealing printed text.  It was very artfully done, but to what end?  If it was something the aliens were trying to conceal from him, they needn’t have bothered—it was going to be quite a while before he could even hope to puzzle out the meanings of the words, assuming they were even going to teach him.  Alternately, it could have been a correction made after the book had been printed.  He had frequently seen that back in the days of printed parts catalogues.  He even had a old catalogue which had a sticker covering the entirety of one page, because it was cheaper than re-printing the whole thing to correct an error.