The addition of new back links is disabled. Existing back links can still be followed. This lets an author lock out back links to obsolete documents or documents currently being revised. Following this item are count lines, each containing a back link. The first character of each back link is a space, followed by the following items.
Back links appear in ascending order of their first word number.
The starting word of the link, counting words after removal of all HTML mark-up tags and punctuation. The first word in the document is word 1. The last word of the link, counting words as above. A link to a single word will have the same first and last word numbers. A unique number, starting at 1, identifying the link.