[[ http://en.wikipedia.org/wiki/Printing_press#cite_note-21 |]]] Another factor conducive to printing arose from the book existing in the format of the codex , which had originated in the Roman period . [ 23 [[ http://en.wikipedia.org/wiki/Printing_press#cite_note-22 |]]] Considered the most important advance in the history of the book prior to printing itself, the codex had completely