^ Very clever. Not unlike the code where two communicants have a copy of the same book and simply find the words they need in it and transmit pages, paragraphs, line numbers, and word numbers to send messages.
Thus,
173 2 7 4 means page 173, paragraph 2, line 7, word 4
and so on. One can even select individual letters and punctuation from the text.
173 2 7 4 2 is the second letter in that word, thereby varying the length of the code set.
Message closes by sending the title of the next book to use --or a newspaper article or whatever.
Some initial in the clear FTF communication is needed to specify the first book or article or website or whatever.
"Pierre has a long moustache. Pierre has a long moustache." :)