Tom Clancy in the book "Patriot games" (1987), p86 at
https://archive.org/details/patriotgamesclan00clan/page/86/m... :
> ... first draft of the report, I came up with an idea to make each one unique."
> "They've been doing that for years," Holmes noted. "All one must do is misplace a comma here and there. Easiest thing in the world. If the newspeople are foolish enough to print a photograph of the document, we can identify the leak."
> "Yes, sir, and the reporters who publish the leaks know that, too. They've learned not to show photographs of the documents they get from their sources, haven't they?" Ryan answered. "What I came up with was a new twist on that. Agents and Agencies has four sections. Each section has a summary paragraph. Each of those is written in a fairly dramatic fashion."
> "Yes, I noticed that," Charleston said. "Didn't read like a CIA document at all. More like one of ours. We use people to write our reports, you see, not computers. Do go on."
> "Each summary paragraph has six different versions, and the mixture of those paragraphs is unique to each numbered copy of the paper. There are over a thousand possible permutations, but only ninety-six numbered copies of the actual document. The reason the summary paragraphs are so -- well, lurid, I guess -- is to entice a reporter to quote them verbatim in the public media. If he quotes something from two or three of those paragraphs, we know which copy he saw and, therefore, who leaked it. They've got an even more refined version of the trap working now. You can do it by computer. You use a thesaurus program to shuffle through synonyms, and you can make every copy of the document totally unique."