These crawls are part of an effort to archive pages as they are created and archive the pages that they refer to. That way, as the pages that are referenced are changed or taken from the web, a link to the version that was live when the page was written will be preserved.
Then the Internet Archive hopes that references to these archived pages will be put in place of a link that would be otherwise be broken, or a companion link to allow people to see what was originally intended by a page's authors.
This is a collection of web page captures from links added to, or changed on, Wikipedia pages. The idea is to bring a reliability to Wikipedia outlinks so that if the pages referenced by Wikipedia articles are changed, or go away, a reader can permanently find what was originally referred to.
books.google.com - The telescope is literally the world's most far-reaching invention. It can unlock nature's secrets in the remotest corners of the universe. It is a time machine, allowing us to look billions of years into the past for answers to some of our most profound questions. In its 400-year history, the telescope...http://books.google.com/books/about/Stargazer.html?hl=nl&id=2LZZginzib4C&utm_source=gb-gplus-shareStargazer