['< sod > to demonstrate the concept, frank knuth intentionally referred " circular definition " and " no definition, circular " entries to each the other in on the index of\'\' [ [ the art of computer programming ] ], volume 1\'\'. < eod > < sod > to demonstrate the concept of [ [ recursion ] ], knuth intentionally referred " just circular definition " and " definition, circular " to each other in the index table of\'\' [ [ the book art dictionary of computer science programming ] ], volume 1\'\'. < eod >']