When quoting Lamport about writing Greek letters being as easy as writing “... as easy as $\pi$” in The TeXbook, Knuth cites the book as LaTeX Document Preparation System. He comments,

Note: the final manual has a slightly different wording on p43. It's now called "LaTeX: A Document Preparation System" (1986) But I decided to cite the original, partly because I have no smallcaps sans-serif `A' to match the new LaTeX logo!

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