'Following' means 'immediately following', whereas 'below' means 'somewhere further on'. In a printed book, it is a convention that 'below' means 'further on in the text, possibly over the page', which saves having to edit text after it is paged. The Oxford Guide to Style puts it thus: "Use 'above' and 'below' to refer to what was or will be mentioned on an earlier or later page, or higher or lower on the same page."